Found 82 papers in cond-mat
Date of feed: Wed, 06 Sep 2023 00:30:00 GMT

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Speeding-up Hybrid Functional based Ab Initio Molecular Dynamics using Multiple Time-stepping and Resonance Free Thermostat. (arXiv:2309.00651v1 [physics.chem-ph])
Ritama Kar, Sagarmoy Mandal, Vaishali Thakkur, Bernd Meyer, Nisanth N. Nair

Ab initio molecular dynamics (AIMD) based on density functional theory (DFT) has become a workhorse for studying the structure, dynamics, and reactions in condensed matter systems. Currently, AIMD simulations are primarily carried out at the level of generalized gradient approximation (GGA), which is at the 2nd rung of DFT-functionals in terms of accuracy. Hybrid DFT functionals which form the 4th rung in the accuracy ladder, are not commonly used in AIMD simulations as the computational cost involved is $100$ times or higher. To facilitate AIMD simulations with hybrid functionals, we propose here an approach that could speed up the calculations by ~30 times or more for systems with a few hundred of atoms. We demonstrate that, by achieving this significant speed up and making the compute time of hybrid functional based AIMD simulations at par with that of GGA functionals, we are able to study several complex condensed matter systems and model chemical reactions in solution with hybrid functionals that were earlier unthinkable to be performed.


Quantum-Geometric Origin of Stacking Ferroelectricity. (arXiv:2309.00728v1 [cond-mat.mtrl-sci])
Benjamin T. Zhou, Vedangi Pathak, Marcel Franz

Stacking ferroelectricity has been discovered in a wide range of van der Waals materials and holds promise for applications, including photovoltaics and high-density memory devices. We show that the microscopic origin of stacking ferroelectric polarization can be generally understood as a consequence of nontrivial Berry phase borne out of an effective Su-Schrieffer-Heeger model description with broken sublattice symmetry, thus uniting novel two-dimensional ferroelectricity with the modern theory of polarization. Our theory applies to known stacking ferroelectrics such as bilayer transition-metal dichalcogenides in 3R and T$_{\rm d}$ phases, as well as general AB-stacked bilayers with honeycomb lattice and staggered sublattice potential. In addition to establishing a unifying microscopic framework for stacking ferroelectrics the quantum-geometric perspective provides key guiding principles for the design of new van der Waals materials with robust ferroelectric polarization.


Microscopic scale of quantum phase transitions: from doped semiconductors to spin chains, cold gases and moir\'e superlattices. (arXiv:2309.00749v1 [cond-mat.str-el])
Andrey Rogachev

In the vicinity of continuous quantum phase transitions (QPTs), quantum systems become scale-invariant and can be grouped into universality classes characterized by sets of critical exponents. We have found that despite scale-invariance and universality, the experimental data still contain information related to the microscopic processes and scales governing QPTs. We conjecture that near QPTs, various physical quantities follow the generic exponential dependence predicted by the scaling theory of localization; this dependence includes as a parameter a microscopic seeding scale of the renormalization group, $L_0$. We also conjecture that for interacting systems, the temperature cuts the renormalization group flow at the length travelled by a system-specific elementary excitation over the life-time set by the Planckian time, $\tau_P$=$\hbar/k_BT$. We have adapted this approach for QPTs in several systems and showed that $L_0$ extracted from experiment is comparable to physically-expected minimal length scales, namely (i) the mean free path for metal-insulator transition in doped semiconductors, (ii) the distance between spins in Heisenberg and Ising chains, (iii) the period of an optical lattice for cold atom boson gases, and (iv) the period of a moir\'e superlattice for the Mott QPT in dichalcogenide bilayers. In the first companion paper, we show that in superconducting films and nanowires, as well as in the high temperature superconductor La$_{1.92}$Sr$_{0.08}$CuO$_4$, $L_0$ is comparable to superconducting coherence length. In the second companion paper, we show that in quantum Hall systems, $L_0$ is comparable to the magnetic length. The developed theoretical approach quantitatively explains and unifies a large body of experimental data and can be expanded to other complex systems


Quantum phase transitions in quantum Hall and other topological systems: role of the Planckian time. (arXiv:2309.00750v1 [cond-mat.str-el])
Andrey Rogachev

Transformations between the plateau states of the quantum Hall effect (QHE) are an archetypical example of quantum phase transitions (QPTs) between phases with non-trivial topological order. These transitions appear to be well-described by the single-particle network theories. The long-standing problem with this approach is that it does not account for Coulomb interactions. In this paper, we show that experimental data in the quantum critical regime for both integer and fractional QHEs can be quantitatively explained by the recently developed phenomenological model of QPTs in interacting systems. This model assumes that all effects of interactions are contained in the life-time of fluctuations as set by the Planckian time $\tau_P=\hbar/k_BT$. The dephasing length is taken as the distance traveled by a non-interacting particle along the bulk edge state over this time. We show that the model also provides quantitative description of QPTs between the ground states of anomalous QHE and axion and Chern insulators. These analyzed systems are connected in that the QPTs occur via quantum percolation. Combining the presented results with the results of two companion papers, we conclude that the Planckian time is the encompassing characteristic of QPTs in interacting systems, independent of dimensionality and microscopic physics.


Magic momenta and three dimensional Landau levels from a three dimensional graphite moir\'e superlattice. (arXiv:2309.00825v1 [cond-mat.mes-hall])
Xin Lu, Bo Xie, Yue Yang, Xiao Kong, Jun Li, Feng Ding, Zhu-Jun Wang, Jianpeng Liu

Twisted bilayer graphene (TBG) and other quasi-two-dimensional moir\'e superlattices have attracted significant attention due to the emergence of various correlated and topological states associated with the flat bands in these systems. In this work, we theoretically explore the physical properties of a new type of \textit{three dimensional graphite moir\'e superlattice}, the bulk alternating twisted graphite (ATG) system with homogeneous twist angle, which is grown by in situ chemical vapor decomposition method. Compared to TBG, the bulk ATG system is bestowed with an additional wavevector degrees of freedom due to the extra dimensionality. As a result, we find that when the twist angle of bulk ATG is smaller than twice of the magic angle of TBG, there always exist ``magic momenta" at which the in-plane Fermi velocities of the moir\'e bands vanish. Moreover, topologically distinct flat bands of TBG at different magic angles can even co-exist at different out-of-plane wavevectors in a single bulk ATG system. Most saliently, when the twist angle is relatively large, exactly dispersionless three dimensional zeroth Landau level would emerge in the bulk ATG, which may give rise to robust three dimensional quantum Hall effects over a large range of twist angles.


Room-Temperature Anomalous Hall Effect in Graphene in Interfacial Magnetic Proximity with EuO Grown by Topotactic Reduction. (arXiv:2309.00892v1 [cond-mat.mtrl-sci])
Satakshi Pandey, Simon Hettler, Raul Arenal, Corinne Bouillet, Aditi Raman Moghe, Stephane Berciaud, Jerome Robert, Jean Francois Dayen, David Halley

We show that thin layers of EuO, a ferromagnetic insulator, can be achieved by topotactic reduction under titanium of a Eu2O3 film deposited on top of a graphene template. The reduction process leads to the formation of a 7-nm thick EuO smooth layer, without noticeable structural changes in the underlying chemical vapor deposited (CVD) graphene. The obtained EuO films exhibit ferromagnetism, with a Curie temperature that decreases with the initially deposited Eu2O3 layer thickness. By adjusting the thickness of the Eu2O3 layer below 7 nm, we promote the formation of EuO at the very graphene interface: the EuO/graphene heterostructure demonstrates the anomalous Hall effect (AHE), which is a fingerprint of proximity-induced spin polarization in graphene. The AHE signal moreover persists above Tc up to 350K due to a robust super-paramagnetic phase in EuO. This original high-temperature magnetic phase is attributed to magnetic polarons in EuO: we propose that the high strain in our EuO films grown on graphene stabilizes the magnetic polarons up to room temperature. This effect is different from the case of bulk EuO in which polarons vanish in the vicinity of the Curie temperature Tc= 69K.


Out-of-plane spin-to-charge conversion at low temperatures in graphene/MoTe$_2$ heterostructures. (arXiv:2309.00984v1 [cond-mat.mes-hall])
Nerea Ontoso, C.K. Safeer, Josep Ingla-Aynés, Franz Herling, Luis E. Hueso, M. Reyes Calvo, Fèlix Casanova

Multi-directional spin-to-charge conversion - in which spin polarizations with different orientations can be converted into a charge current in the same direction - has been demonstrated in low-symmetry materials and interfaces. This is possible because, in these systems, spin to charge conversion can occur in unconventional configurations in which spin polarization and charge current where charge current, spin current and polarization do not need to be mutually orthogonal. Here, we explore, in the low temperature regime, the spin-to-charge conversion in heterostructures of graphene with the low-symmetry 1T' phase of MoTe$_2$. First, we observe the emergence of charge conversion for out-of-plane spins at temperatures below 100 K. This unconventional component is allowed by the symmetries of both MoTe$_2$ and graphene and likely arises from spin Hall effect in the spin-orbit proximitized graphene. Moreover, we examine the low-temperature evolution of non-local voltage signals arising from the charge conversion of the two in-plane spin polarizations, which have been previously observed at higher temperature. As a result, we report omni-directional spin-to-charge conversion - for all spin polarization orientations - in graphene/MoTe${_2}$ heterostructures at low temperatures.


Size effects on atomic collapse in the dice lattice. (arXiv:2309.01023v1 [cond-mat.str-el])
D. O. Oriekhov, S. O. Voronov

We study the role of size effects on atomic collapse of charged impurity in the flat band system. The tight-binding simulations are made for the dice lattice with circular quantum dot shapes. It is shown that the mixing of in-gap edge states with bound states in impurity potential leads to increasing the critical charge value. This effect, together with enhancement of gap due to spatial quantization, makes it more difficult to observe the dive-into-continuum phenomenon in small quantum dots. At the same time, we show that if in-gap states are filled, the resonant tunneling to bound state in the impurity potential might occur at much smaller charge, which demonstrates non-monotonous dependence with the size of sample lattice. In addition, we study the possibility of creating supercritical localized potential well on different sublattices, and show that it is possible only on rim sites, but not on hub site. The predicted effects are expected to naturally occur in artificial flat band lattices.


"Extraordinary" Phase Transition Revealed in a van der Waals Antiferromagnet. (arXiv:2309.01047v1 [cond-mat.mtrl-sci])
Xiaoyu Guo, Wenhao Liu, Jonathan Schwartz, Suk Hyun Sung, Dechen Zhang, Makoto Shimizu, Aswin L. N. Kondusamy, Lu Li, Kai Sun, Hui Deng, Harald O. Jeschke, Igor I. Mazin, Robert Hovden, Bing Lv, Liuyan Zhao

While the surface-bulk correspondence has been ubiquitously shown in topological phases, the relationship between surface and bulk in Landau-like phases is much less explored. Theoretical investigations since 1970s for semi-infinite systems have predicted the possibility of the surface order emerging at a higher temperature than the bulk, clearly illustrating a counterintuitive situation and greatly enriching phase transitions. But experimental realizations of this prediction remain missing. Here, we demonstrate the higher-temperature surface and lower-temperature bulk phase transitions in CrSBr, a van der Waals (vdW) layered antiferromagnet. We leverage the surface sensitivity of electric dipole second harmonic generation (SHG) to resolve surface magnetism, the bulk nature of electric quadrupole SHG to probe bulk spin correlations, and their interference to capture the two magnetic domain states. Our density functional theory calculations show the suppression of ferromagnetic-antiferromagnetic competition at the surface responsible for this enhanced surface magnetism. Our results not only show unexpected, richer phase transitions in vdW magnets, but also provide viable ways to enhance magnetism in their 2D form.


Orbital-Dependent Electron Correlation in Double-Layer Nickelate La3Ni2O7. (arXiv:2309.01148v1 [cond-mat.supr-con])
Jiangang Yang, Hualei Sun, Xunwu Hu, Yuyang Xie, Taimin Miao, Hailan Luo, Hao Chen, Bo Liang, Wenpei Zhu, Gexing Qu, Cui-Qun Chen, Mengwu Huo, Yaobo Huang, Shenjin Zhang, Fengfeng Zhang, Feng Yang, Zhimin Wang, Qinjun Peng, Hanqing Mao, Guodong Liu, Zuyan Xu, Tian Qian, Dao-Xin Yao, Meng Wang, Lin Zhao, X. J. Zhou

The latest discovery of high temperature superconductivity near 80K in La3Ni2O7 under high pressure has attracted much attention. Many proposals are put forth to understand the origin of superconductivity. The determination of electronic structures is a prerequisite to establish theories to understand superconductivity in nickelates but is still lacking. Here we report our direct measurement of the electronic structures of La3Ni2O7 by high-resolution angle-resolved photoemmission spectroscopy. The Fermi surface and band structures of La3Ni2O7 are observed and compared with the band structure calculations. A flat band is formed from the Ni-3dz2 orbitals around the zone corner which is 50meV below the Fermi level. Strong electron correlations are revealed which are orbital- and momentum-dependent. Our observations will provide key information to understand the origin of high temperature superconductivity in La3Ni2O7.


Generalized Majorana edge modes in a number-conserving periodically driven $p$-wave superconductor. (arXiv:2309.01163v1 [cond-mat.mes-hall])
Raditya Weda Bomantara

We study an analytically solvable and experimentally relevant number-conserving periodically driven $p$-wave superconductor. Such a system is found to support generalized Majorana zero and $\pi$ modes which, despite being non-Hermitian, are still capable of encoding qubits. Moreover, appropriate winding numbers characterizing the topology of such generalized Majorana modes are defined and explicitly calculated. We further discuss the fate of the obtained generalized Majorana modes in the presence of finite charging energy. Finally, we shed light on the quantum computing prospects of such modes by demonstrating the robustness of their encoded qubits and explicitly braiding a pair of generalized Majorana modes.


Observation of multiple flat bands and topological Dirac states in a new titanium based slightly distorted kagome metal YbTi3Bi4. (arXiv:2309.01176v1 [cond-mat.mes-hall])
Anup Pradhan Sakhya, Brenden R. Ortiz, Barun Ghosh, Milo Sprague, Mazharul Islam Mondal, Matthew Matzelle, Iftakhar Bin Elius, Nathan Valadez, David G. Mandrus, Arun Bansil, Madhab Neupane

Kagome lattices have emerged as an ideal platform for exploring various exotic quantum phenomena such as correlated topological phases, frustrated lattice geometry, unconventional charge density wave orders, Chern quantum phases, superconductivity, etc. In particular, the vanadium based nonmagnetic kagome metals AV3Sb5 (A= K, Rb, and Cs) have seen a flurry of research interest due to the discovery of multiple competing orders. Here, we report the discovery of a new Ti based kagome metal YbTi3Bi4 and employ angle-resolved photoemission spectroscopy (ARPES), magnetotransport in combination with density functional theory calculations to investigate its electronic structure. We reveal spectroscopic evidence of multiple flat bands arising from the kagome lattice of Ti with predominant Ti 3d character. Through our calculations of the Z2 indices, we have identified that the system exhibits topological nontriviality with surface Dirac cones at the Gamma point and a quasi two-dimensional Dirac state at the K point which is further confirmed by our ARPES measured band dispersion. These results establish YbTi3Bi4 as a novel platform for exploring the intersection of nontrivial topology, and electron correlation effects in this newly discovered Ti based kagome lattice.


Direct visualization of electric current induced dipoles of atomic impurities. (arXiv:2309.01182v1 [cond-mat.mes-hall])
Yaowu Liu, Zichun Zhang, Sidan Chen, Shengnan Xu, Lichen Ji, Wei Chen, Xinyu Zhou, Jiaxin Luo, Xiaopen Hu, Wenhui Duan, Xi Chen, Qi-Kun Xue, Shuai-Hua Ji

Learning the electron scattering around atomic impurities is a fundamental step to fully understand the basic electronic transport properties of realistic conducting materials. Although many efforts have been made in this field for several decades, atomic scale transport around single point-like impurities has yet been achieved. Here, we report the direct visualization of the electric current induced dipoles around single atomic impurities in epitaxial bilayer graphene by multi-probe low temperature scanning tunneling potentiometry as the local current density is raised up to around 25 A/m, which is considerably higher than that in previous studies. We find the directions of these dipoles which are parallel or anti-parallel to local current are determined by the charge polarity of the impurities, revealing the direct evidence for the existence of the carrier density modulation effect proposed by Landauer in 1976. Furthermore, by $in$ $situ$ tuning local current direction with contact probes, these dipoles are redirected correspondingly. Our work paves the way to explore the electronic quantum transport phenomena at single atomic impurity level and the potential future electronics toward or beyond the end of Moore's Law.


The role of pressure-induced stacking faults on the magnetic properties of gadolinium. (arXiv:2309.01285v1 [cond-mat.mtrl-sci])
Rafael Martinho Vieira, Olle Eriksson, Torbjörn Björkman, Ondřej Šipr, Heike C. Herper

Experimental data show that under pressure, Gd goes through a series of structural transitions hcp to Sm-type (close-packed rhombohedral) to dhcp that is accompanied by a gradual decrease of the Curie temperature and magnetization till the collapse of a finite magnetization close to the dhcp structure. We explore theoretically the pressure-induced changes of the magnetic properties, by describing these structural transitions as the formation of fcc stackings faults. Using this approach, we are able to describe correctly the variation of the Curie temperature with pressure, in contrast to a static structural model using the hcp structure.


Steering-induced phase transition in measurement-only quantum circuits. (arXiv:2309.01315v1 [quant-ph])
Dongheng Qian, Jing Wang

Competing measurements alone can give rise to distinct phases characterized by entanglement entropy$\unicode{x2013}$such as the volume law phase, symmetry-breaking (SB) phase, and symmetry-protected topological (SPT) phase$\unicode{x2013}$that can only be discerned through quantum trajectories, making them challenging to observe experimentally. In another burgeoning area of research, recent studies have demonstrated that steering can give rise to additional phases within quantum circuits. In this work, we show that new phases can appear in measurement-only quantum circuit with steering. Unlike conventional steering methods that rely solely on local information, the steering scheme we introduce requires the circuit's structure as an additional input. These steering induced phases are termed as "informative" phases. They are distinguished by the intrinsic dimension of the bitstrings measured in each circuit run, making them substantially easier to detect in experimental setups. We explicitly show this phase transition by numerical simulation in three circuit models that are previously well-studied: projective transverse field Ising model, lattice gauge-Higgs model and XZZX model. When the informative phase coincides with the SB phase, our steering mechanism effectively serves as a "pre-selection" routine, making the SB phase more experimentally accessible. Additionally, an intermediate phase may manifest, where a discrepancy arises between the quantum information captured by entanglement entropy and the classical information conveyed by bitstrings. Our findings demonstrate that steering not only adds theoretical richness but also offers practical advantages in the study of measurement-only quantum circuits.


From orthogonal link to phase vortex in generalized dynamical Hopf insulators. (arXiv:2309.01344v1 [cond-mat.str-el])
Yuxuan Ma, Xin Li, Yu Wang, Shuncai Zhao, Guangqin Xiong, Tongxin Sun

In the creation of Hopf topological matters, the old paradigm is to conceive the Hopf invariant first, and then display its intuitive topology through links. Here we brush aside this effort and put forward a new recipe for unraveling the quenched two-dimensional (2D) two-band Chern insulators under a parallel quench protocol, which implies that the quench quantities with different momentum k are parallel or antiparallel to each other. We find that whether the dynamical Hopf invariant exists or not, the links in (2+1)D space always keep their standard shape even for topological initial states, and trace out the trajectories of phase vortices. The linking number is exactly equal to the difference between pre- and post-quench Chern numbers regardless of the construction of homotopy groups. We employ two concrete examples to illustrate these results, highlighting the polarity reversal at fixed points.


Piezoelectric Electrostatic Superlattices in Monolayer MoS$_2$. (arXiv:2309.01347v1 [cond-mat.mtrl-sci])
Ashwin Ramasubramaniam, Doron Naveh

Modulation of electronic properties of materials by electric fields is central to the operation of modern semiconductor devices, providing access to complex electronic behaviors and greater freedom in tuning the energy bands of materials. Here, we explore one-dimensional superlattices induced by a confining electrostatic potential in monolayer MoS$_2$, a prototypical two-dimensional semiconductor. Using first-principles calculations, we show that periodic potentials applied to monolayer MoS$_2$ induce electrostatic superlattices in which the response is dominated by structural distortions relative to purely electronic effects. These structural distortions reduce the intrinsic band gap of the monolayer substantially while also polarizing the monolayer through piezoelectric coupling, resulting in spatial separation of charge carriers as well as Stark shifts that produce dispersive minibands. Importantly, these minibands inherit the valley-selective magnetic properties of monolayer MoS$_2$, enabling fine control over spin-valley coupling in MoS$_2$ and similar transition-metal dichalcogenides.


Classification of Lifshitz invariant in multiband superconductors: an application to Leggett modes in the linear response regime in Kagome lattice models. (arXiv:2309.01410v1 [cond-mat.supr-con])
Raigo Nagashima, Sida Tian, Rafael Haenel, Naoto Tsuji, Dirk Manske

Multiband superconductors are sources of rich physics arising from multiple order parameters, which show unique collective dynamics including Leggett mode as relative phase oscillations. Previously, it has been pointed out that the Leggett mode can be optically excited in the linear response regime, as demonstrated in a one-dimensional model for multiband superconductors[T. Kamatani, et al., Phys. Rev. B 105, 094520 (2022)]. Here we identify the linear coupling term in the Ginzburg-Landau free energy to be the so-called Lifshitz invariant, which takes a form of $\boldsymbol{d}\cdot\left(\Psi^{*}_{i}\nabla\Psi_{j} - \Psi_{j}\nabla\Psi^{*}_{i}\right)$, where $\boldsymbol{d}$ is a constant vector and $\Psi_{i}$ and $\Psi_{j}$ $(i\neq j)$ represent superconducting order parameters. We have classified all pairs of irreducible representations of order parameters in the crystallographic point groups that allow for the existence of the Lifshitz invariant. We emphasize that the Lifshitz invariant can appear even in systems with inversion symmetry. The results are applied to a model of $s$-wave superconductors on a Kagome lattice with various bond orders, for which in some cases we confirm that the Leggett mode appears as a resonance peak in a linear optical conductivity spectrum based on microscopic calculations. We discuss a possible experimental observation of the Leggett mode by a linear optical response in multiband superconductors.


One-dimensional topological channels in heterostrained bilayer graphene. (arXiv:2309.01467v1 [cond-mat.mes-hall])
Nina C. Georgoulea, Nuala M. Caffrey, Stephen R. Power

The domain walls between AB- and BA-stacked gapped bilayer graphene have garnered intense interest as they host topologically-protected, valley-polarised transport channels. The introduction of a twist angle between the bilayers and the associated formation of a Moire pattern has been the dominant method used to study these topological channels, but heterostrain can also give rise to similar stacking domains and interfaces. Here, we theoretically study the electronic structure of a uniaxially heterostrained bilayer graphene. We discuss the formation and evolution of interface-localized channels in the one-dimensional Moire pattern that emerges due to the different stacking registries between the two layers. We find that a uniform heterostrain is not sufficient to create one-dimensional topological channels in biased bilayer graphene. Instead, using a simple model to account for the in-plane atomic reconstruction driven by the changing stacking registry, we show that the resulting expanded Bernal-stacked domains and sharper interfaces are required for robust topological interfaces to emerge. These states are highly localised in the AA- or SP-stacked interface regions and exhibit differences in their layer and sublattice distribution depending on the interface stacking. We conclude that heterostrain can be used as a mechanism to tune the presence and distribution of topological channels in gapped bilayer graphene systems, complementary to the field of twistronics.


Acoustic realization of projective mirror Chern insulators. (arXiv:2309.01484v1 [cond-mat.mes-hall])
Tianzi Li, Luohong Liu, Qicheng Zhang, Chunyin Qiu

Symmetry plays a key role in classifying topological phases. Recent theory shows that in the presence of gauge fields, the algebraic structure of crystalline symmetries needs to be projectively represented, which enables unprecedented topological band physics. Here, we report a concrete acoustic realization of mirror Chern insulators by exploiting the concept of projective symmetry. More specifically, we introduce a simple but universal recipe for constructing projective mirror symmetry, and conceive a minimal model for achieving the projective symmetry-enriched mirror Chern insulators. Based on our selective-excitation measurements, we demonstrate unambiguously the projective mirror eigenvalue-locked topological nature of the bulk states and associated chiral edge states. More importantly, we extract the non-abelian Berry curvature and identify the mirror Chern number directly, as conclusive experimental evidence for this exotic topological phase. All experimental results agree well with the theoretical predictions. Our findings will shine new light on the topological systems equipped with gauge fields.


Engineering rich two-dimensional higher-order topological phases by flux and periodic driving. (arXiv:2309.01499v1 [cond-mat.mes-hall])
Ming-Jian Gao, Jun-Hong An

Nodal-line semimetal is commonly believed to exist in $\mathcal{PT}$ symmetric or mirror-rotation symmetric systems. Here, we find a flux-induced parameter-dimensional second-order nodal-line semimetal (SONLS), which has the coexisting hinge Fermi arcs and drumhead surface states, in a two-dimensional system without $\mathcal{PT}$ and mirror-rotation symmetries. Meanwhile, we discover a flux-induced second-order topological insulator (SOTI). Then we artificially create exotic hybrid-order nodal-line semimetals with fruitful nodal-line structures hosted by different quasienergy gaps and widely tunable numbers of corner states by applying a periodic driving on our SONLS and SOTI, respectively. Such Floquet engineered high tunability of the orders and the nodal-line structures of the SONLS and the corner-state number of SOTI sets up a foundation on exploring their further applications.


Sublimation of silicene and thin silicon films: a view from molecular dynamics simulation. (arXiv:2309.01521v1 [cond-mat.mtrl-sci])
Yu. D. Fomin, E. N. Tsiok, V. N. Ryzhov

A molecular dynamics simulation of sublimation of silicene and silicon films of different thikness is performed. It is shown that thiner films sublimate at lower temperatures. The sublimation temperature comes to a saturated value of $T=1725$ K at the films thiker than $16$ atomc layers. These results are consistent with the surface mediated collaps of the crystal structure. At the same time this mechanism is different from the crystal structure collapse of graphite and graphene.


Giant ultra-broadband photoconductivity in twisted graphene heterostructures. (arXiv:2309.01555v1 [cond-mat.mes-hall])
Hitesh Agarwal, Krystian Nowakowski, Andres Forrer, Alessandro Principi, Riccardo Bertini, Sergi Batlle-Porro, Antoine Reserbat-Plantey, Parmeshwar Prasad, Lorenzo Vistoli, Kenji Watanabe, Takashi Taniguchi, Adrian Bachtold, Giacomo Scalari, Roshan Krishna Kumar, Frank H.L. Koppens

The requirements for broadband photodetection are becoming exceedingly demanding in hyperspectral imaging. Whilst intrinsic photoconductor arrays based on mercury cadmium telluride represent the most sensitive and suitable technology, their optical spectrum imposes a narrow spectral range with a sharp absorption edge that cuts their operation to < 25 um. Here, we demonstrate a giant ultra-broadband photoconductivity in twisted double bilayer graphene heterostructures spanning a spectral range of 2 - 100 um with internal quantum efficiencies ~ 40 % at speeds of 100 kHz. The giant response originates from unique properties of twist-decoupled heterostructures including pristine, crystal field induced terahertz band gaps, parallel photoactive channels, and strong photoconductivity enhancements caused by interlayer screening of electronic interactions by respective layers acting as sub-atomic spaced proximity screening gates. Our work demonstrates a rare instance of an intrinsic infrared-terahertz photoconductor that is complementary metal-oxide-semiconductor compatible and array integratable, and introduces twist-decoupled graphene heterostructures as a viable route for engineering gapped graphene photodetectors with 3D scalability.


On the self-consistent Landauer-B\"uttikker formalism. (arXiv:2309.01564v1 [math-ph])
Horia D. Cornean, Giovanna Marcelli

We provide sufficient conditions such that the time evolution of a mesoscopic tight-binding open system with a local Hartree-Fock non-linearity converges to a self-consistent non-equilibrium steady state, which is independent of the initial condition from the "small sample". We also show that the steady charge currents are given by Landauer-B\"uttikker-like formulas, and make the connection with the case of weakly self-interacting many-body systems.


Layer Construction of Three-Dimensional Z2 Monopole Charge Nodal Line Semimetals and prediction of the abundant candidate materials. (arXiv:2309.01566v1 [cond-mat.mtrl-sci])
Yongpan Li, Shifeng Qian, Cheng-Cheng Liu

The interplay between symmetry and topology led to the concept of symmetry-protected topological states, including all non-interacting and weakly interacting topological quantum states. Among them, recently proposed nodal line semimetal states with space-time inversion ($\mathcal{PT}$) symmetry which are classified by the Stiefel-Whitney characteristic class associated with real vector bundles and can carry a nontrivial $\mathbb{Z}_2$ monopole charge have attracted widespread attention. However, we know less about such 3D $\mathbb{Z}_2$ nodal line semimetals and do not know how to construct them. In this work, we first extend the layer construction previously used to construct topological insulating states to topological semimetallic systems. We construct 3D $\mathbb{Z}_2$ nodal line semimetals by stacking of 2D $\mathcal{PT}$-symmetric Dirac semimetals via nonsymmorphic symmetries. Based on our construction scheme, effective model and combined with first-principles calculations, we predict two types of candidate electronic materials for $\mathbb{Z}_2$ nodal line semimetals, namely 14 Si and Ge structures and 108 transition metal dichalcogenides $MX_2$ ($M$=Cr, Mo, W, $X$=S, Se, Te). Our theoretical construction scheme can be directly applied to metamaterials and circuit systems. Our work not only greatly enriches the candidate materials and deepens the understanding of $\mathbb{Z}_2$ nodal line semimetal states but also significantly extends the application scope of layer construction.


Direct observation of topological surface states in the layered kagome lattice with broken time-reversal symmetry. (arXiv:2309.01579v1 [cond-mat.str-el])
Zhicheng Jiang, Tongrui Li, Jian Yuan, Zhengtai Liu, Zhipeng Cao, Soohyun Cho, Mingfang Shu, Yichen Yang, Jianyang Ding, Zhikai Li, Jiayu Liu, Zhonghao Liu, Jishan Liu, Jie Ma, Zhe Sun, Yanfeng Guo, Dawei Shen

Magnetic topological quantum materials display a diverse range of fascinating physical properties which arise from their intrinsic magnetism and the breaking of time-reversal symmetry. However, so far, few examples of intrinsic magnetic topological materials have been confirmed experimentally, which significantly hinder our comprehensive understanding of the abundant physical properties in this system. The kagome lattices, which host diversity of electronic structure signatures such as Dirac nodes, flat bands, and saddle points, provide an alternative and promising platform for in-depth investigations into correlations and band topology. In this article, drawing inspiration from the stacking configuration of MnBi$_2$Te$_4$, we conceive and then synthesize a high-quality single crystal EuTi$_3$Bi$_4$, which is a unique natural heterostructure consisting of both topological kagome layers and magnetic interlayers. We investigate the electronic structure of EuTi$_3$Bi$_4$ and uncover distinct features of anisotropic multiple Van Hove singularitie (VHS) that might prevent Fermi surface nesting, leading to the absence of a charge density wave (CDW). In addition, we identify the topological nontrivial surface states that serve as connections between different saddle bands in the vicinity of the Fermi level. Combined with calculations, we establish that, the effective time-reversal symmetry S=$\theta$$\tau_{1/2}$ play a crucial role in the antiferromagnetic ground state of EuTi$_3$Bi$_4$, which ensures the stability of the topological surface states and gives rise to their intriguing topological nature. Therefore, EuTi$_3$Bi$_4$ offers the rare opportunity to investigate correlated topological states in magnetic kagome materials.


Exchange spin-orbit coupling and unconventional p-wave magnetism. (arXiv:2309.01607v1 [cond-mat.mes-hall])
Anna Birk Hellenes, Tomáš Jungwirth, Jairo Sinova, Libor Šmejkal

Spin-orbit coupling arising from the relativistic Dirac equation underpins fundamental and applied research areas such as the spin Hall effects and topological insulators. This Dirac mechanism of spin-orbit coupling induces in non-centrosymmetric crystals a momentum-dependent spin splitting typically limited to a meV scale unless involving heavy and often toxic elements. Here we identify a previously overlooked mechanism that shares with the Dirac mechanism the characteristic signature of spin-orbit coupling, namely the antisymmetric time-reversal-invariant spin polarization in the band structure. In contrast to the relativistic Dirac equation, our spin-orbit coupling arises from the magnetic exchange interaction in non-centrosymmetric crystals with a non-coplanar spin order. An unconventional p-wave magnetic phase, corresponding to this exchange spin-orbit coupling, represents a long-sought but elusive realization of a magnetic counterpart of the p-wave phase of superfluid He-3. We identify type-A exchange spin-orbit coupling realized on mutually-shifted opposite-spin Fermi surfaces, and type-B on one Fermi surface. We predict giant spin splitting magnitudes on the scale of hundreds of meV in realistic material candidates, namely in antiperovskite Ce$_3$InN and Mn$_3$GaN. Our results open a possibility for realizing large exchange spin-orbit coupling phenomena in materials comprising abundant light elements and with implications in fields ranging from spintronics, dissipationless nanoelectronics and quantum electronics, to topological matter.


Kinkless electronic junction along one dimensional electronic channel. (arXiv:2309.01648v1 [cond-mat.str-el])
Qirong Yao, Jae Whan Park, Choongjae Won, Sang-Wook Cheong, Han Woong Yeom

Here we report the formation of type-A and type-B electronic junctions without any structural discontinuity along a well-defined 1-nm-wide one-dimensional electronic channel within a van der Waals layer. We employ scanning tunneling microscopy and spectroscopy techniques to investigate the atomic and electronic structure along peculiar domain walls formed on the charge-density-wave phase of 1T-TaS2. We find distinct kinds of abrupt electronic junctions with discontinuities of the band gap along the domain walls, which do not have any structural kinks and defects. Our density-functional calculations reveal a novel mechanism of the electronic junction formation; they are formed by a kinked domain wall in the layer underneath through substantial electronic interlayer coupling. This work demonstrates that the interlayer electronic coupling can be an effective control knob over several-nanometer-scale electronic property of two-dimensional atomic monolayers.


Nonequilibrium capillary self-assembly. (arXiv:2309.01668v1 [cond-mat.soft])
Stuart J. Thomson, Jack-William Barotta, Daniel M. Harris

Macroscopic objects supported by surface tension at the fluid interface can self-assemble through the action of capillary forces arising from interfacial deformations. The resulting self-assembled structures are ordered but remain trapped in one of potentially many metastable states in the capillary energy landscape. This contrasts with microscopic colloidal self-assembly where thermal fluctuations excite transitions between geometrically distinct ground-state configurations. We herein utilize supercritical Faraday waves to drive structural rearrangements between metastable states of few-particle clusters of millimetric spheres bound by capillary attractions at the fluid interface. Using a combination of experiments and theoretical modelling, we demonstrate how the occupation probabilities of different cluster topologies and transition statistics are controlled by the level of the vibrational forcing and the spatial extent of long-range capillary forces. Our results demonstrate how self-assembly dynamics and statistics may be manipulated across scales by controlling the strength of fluctuations and by tuning the properties of the particle interaction-potential.


Flat-band and multi-dimensional fermions in Pb10(PO4)6O4. (arXiv:2309.01755v1 [cond-mat.mtrl-sci])
Botao Fu, Qin He, Xiao-Ping Li

Employing a combination of first-principles calculations and low-energy effective models, we present a comprehensive investigation on the electronic structure of Pb$_{10}$(PO$_{4}$)$_{6}$O$_{4}$, which exhibits remarkable quasi-one-dimensional flat-band around the Fermi level that contains novel multi-dimensional fermions. These flat bands predominantly originate from $p_x/p_y$ orbital of the oxygen molecules chain at $4e$ Wyckoff positions, and thus can be well-captured by a four-band tight-binding model. Furthermore, the abundant crystal symmetry inherent to Pb$_{10}$(PO$_{4}$)$_{6}$O$_{4}$ provides an ideal platform for the emergence of various multi-dimensional fermions, including a 0D four-fold degenerated Dirac fermion with quadratic dispersion, a 1D quadratic/linear nodal-line (QNL/LNL) fermion along symmetric $k$-paths, 1D hourglass nodal-line (HNL) fermion linked to the Dirac fermion, and a 2D symmetry-enforced nodal surface (NS) found on the $k_z$=$\pi$ plane. Moreover, when considering the weak ferromagnetic order, Pb$_{10}$(PO$_{4}$)$_{6}$O$_{4}$ transforms into a rare semi-half-metal, which is characterized by the presence of Dirac fermion and HNL fermion at the Fermi level for a single spin channel exhibiting 100$\%$ spin polarization. Our findings reveal the coexistence of flat bands, diverse topological semimetal states and ferromagnetism within in Pb$_{10}$(PO$_{4}$)$_{6}$O$_{4}$, which may provide valuable insights for further exploring intriguing interplay between superconductivity and exotic electronic states.


Impact of electrostatic crosstalk on spin qubits in dense CMOS quantum dot arrays. (arXiv:2309.01849v1 [cond-mat.mes-hall])
Jesus D. Cifuentes, Tuomo Tanttu, Paul Steinacker, Santiago Serrano, Ingvild Hansen, James P. Slack-Smith, Will Gilbert, Jonathan Y. Huang, Ensar Vahapoglu, Ross C. C. Leon, Nard Dumoulin Stuyck, Kohei Itoh, Nikolay Abrosimov, Hans-Joachim Pohl, Michael Thewalt, Arne Laucht, Chih Hwan Yang, Christopher C. Escott, Fay E. Hudson, Wee Han Lim, Rajib Rahman, Andrew S. Dzurak, Andre Saraiva

Quantum processors based on integrated nanoscale silicon spin qubits are a promising platform for highly scalable quantum computation. Current CMOS spin qubit processors consist of dense gate arrays to define the quantum dots, making them susceptible to crosstalk from capacitive coupling between a dot and its neighbouring gates. Small but sizeable spin-orbit interactions can transfer this electrostatic crosstalk to the spin g-factors, creating a dependence of the Larmor frequency on the electric field created by gate electrodes positioned even tens of nanometers apart. By studying the Stark shift from tens of spin qubits measured in nine different CMOS devices, we developed a theoretical frawework that explains how electric fields couple to the spin of the electrons in increasingly complex arrays, including those electric fluctuations that limit qubit dephasing times $T_2^*$. The results will aid in the design of robust strategies to scale CMOS quantum technology.


Andreev reflection of quantum Hall states through a quantum point contact. (arXiv:2309.01856v1 [cond-mat.mes-hall])
Mehdi Hatefipour, Joseph J. Cuozzo, Enrico Rossi, Javad Shabani

We investigate the interplay between the quantum Hall (QH) effect and superconductivity in InAs surface quantum well (SQW)/NbTiN heterostructures using a quantum point contact (QPC). We use QPC to control the proximity of the edge states to the superconductor. By measuring the upstream and downstream resistances of the device, we investigate the efficiency of Andreev conversion at the InAs/NbTiN interface. Our experimental data is analyzed using the Landauer-Buttiker formalism, generalized to allow for Andreev reflection processes. We show that by varying the voltage of the QPC, $V_{QPC}$, the average Andreev reflection, $A$, at the QH-SC interface can be tuned from 50% to 10%. The evolution of $A$ with $V_{QPC}$ extracted from the measurements exhibits plateaus separated by regions for which $A$ varies continuously with $V_{QPC}$. The presence of plateaus suggests that for some ranges of $V_{QPC}$ the QPC might be pinching off almost completely from the QH-SC interface some of the edge modes. Our work shows a new experimental setup to control and advance the understanding of the complex interplay between superconductivity and QH effect in two-dimensional gas systems.


Control of Mechanical and Fracture Properties in Two-phase Materials Reinforced by Continuous, Irregular Networks. (arXiv:2309.01888v1 [cond-mat.mtrl-sci])
Tommaso Magrini, Chelsea Fox, Adeline Wihardja, Athena Kolli, Chiara Daraio

Composites with high strength and high fracture resistance are desirable for structural and protective applications. Most composites, however, suffer from poor damage tolerance and are prone to unpredictable fractures. Understanding the behavior of materials with an irregular reinforcement phase offers fundamental guidelines for tailoring their performance. Here, we study the fracture nucleation and propagation in two phase composites, as a function of the topology of their irregular microstructures. We use a stochastic algorithm to design the polymeric reinforcing network, achieving independent control of topology and geometry of the microstructure. By tuning the local connectivity of isodense tiles and their assembly into larger structures, we tailor the mechanical and fracture properties of the architected composites, at the local and global scale. Finally, combining different reinforcing networks into a spatially determined meso-scale assembly, we demonstrate how the spatial propagation of fractures in architected composite materials can be designed and controlled a priori.


Para-fusion Category and Topological Defect Lines in $\mathbb Z_N$-parafermionic CFTs. (arXiv:2309.01914v1 [hep-th])
Jin Chen, Babak Haghighat, Qing-Rui Wang

We study topological defect lines (TDLs) in two-dimensional $\mathbb Z_N$-parafermoinic CFTs. Different from the bosonic case, in the 2d parafermionic CFTs, there exist parafermionic defect operators that can live on the TDLs and satisfy interesting fractional statistics. We propose a categorical description for these TDLs, dubbed as ``para-fusion category", which contains various novel features, including $\mathbb Z_M$ $q$-type objects for $M\vert N$, and parafermoinic defect operators as a type of specialized 1-morphisms of the TDLs. The para-fusion category in parafermionic CFTs can be regarded as a natural generalization of the super-fusion category for the description of TDLs in 2d fermionic CFTs. We investigate these distinguishing features in para-fusion category from both a 2d pure CFT perspective, and also a 3d anyon condensation viewpoint. In the latter approach, we introduce a generalized parafermionic anyon condensation, and use it to establish a functor from the parent fusion category for TDLs in bosonic CFTs to the para-fusion category for TDLs in the parafermionized ones. At last, we provide many examples to illustrate the properties of the proposed para-fusion category, and also give a full classification for a universal para-fusion category obtained from parafermionic condensation of Tambara-Yamagami $\mathbb Z_N$ fusion category.


Cavity-induced topological edge and corner states. (arXiv:2309.01927v1 [cond-mat.mes-hall])
Motohiko Ezawa

We investigate a two-level system with alternating XX coupling in a photon cavity. It is mapped to a free boson model equally coupled to a photon, whose interaction is highly nonlocal. Some intriguing topological phenomena emerge as a function of the photon coupling. The photon energy level anticrosses the zero-energy topological edges at a certain photon coupling, around which the symmetric edge state acquires nonzero energy due to the mixing with the photon. Furthermore, the photon state is transformed into the topological zero-energy edge or corner state when the photon coupling is strong enough. It is a cavity-induced topological edge or corner state. On the other hand, the other topological edge or corner states do not couple with the photon and remains at zero energy even in the presence of the cavity. We analyze a cavity-induced topological edge state in the Su-Schrieffer-Heeger model and a cavity-induced topological corner state in the breathing Kagome model.


Na-catalyzed rapid synthesis and characterization of intercalated graphite CaC6. (arXiv:2309.01942v1 [cond-mat.mtrl-sci])
Akira Iyo (1), Hiroshi Fujihisa (1), Yoshito Gotoh (1), Shigeyuki Ishida (1), Hiroshi Eisaki (1), Hiraku Ogino (1), Kenji Kawashima (1 and 2) ((1) National Institute of Advanced Industrial Science and Technology (AIST) (2) IMRA JAPAN Co., Ltd)

In this study, we conducted experiments on CaC6 for elucidating the Na-catalyzed formation mechanism and achieving rapid mass synthesis of graphite intercalation compounds (GICs). Rapidly synthesized CaC6 was characterized by analysis of its crystal structure and physical properties. We found that the formation of the reaction intermediate Na-GIC (NaCx, x = 64) requires a larger amount of Na than is intercalated between the graphite interlayers. The requirement for excess Na may provide insights into the mechanism of Na-catalyzed GIC formation. A Na-to-C molar mixing ratio of 1.5-2.0:6 was suitable for the efficient formation of CaC6 under heat treatment at 250{\deg}C for 2 h, and the catalytic Na remaining in the sample was demonstrably reduced to a Na:Ca ratio of approximately 3:97. The upper critical field Hc2 was enhanced approximately three times compared to those of previous reports. Based on X-ray diffraction and experimental parameter analysis, we concluded that the enhancement of Hc2 was attributed to the disordered stacking sequence in CaC6, possibly because of the rapid and low-temperature formation. Physical properties derived from specific heat measurements were comparable to those of high-quality CaC6, which is slowly synthesized using the molten Li-Ca alloy method. This study provides new avenues for future research and exploration in the rapid mass synthesis of GICs as practical materials, for applications such as battery electrodes and superconducting wires.


Rapid droplet leads the Liquid-Infused Slippery Surfaces more slippery. (arXiv:2309.02038v1 [physics.flu-dyn])
Kun Li, Cunjing Lv, Xi-Qiao Feng

The introduction of lubricant between fluid and substrate endows the Liquid-Infused Slippery Surfaces with excellent wetting properties: low contact angle, various liquids repellency, ice-phobic and self-healing. Droplets moving on such surfaces have been widely demonstrated to obey a Landau-Levich-Derjaguin (LLD) friction. Here, we show that this power law is surprisingly decreased with the droplet accelerates: in the rapid droplet regime, the slippery surfaces seem more slippery than LLD friction. Combining experimental and numerical techniques, we find that the meniscus surrounding the droplet exhibits an incompletely developed state. The Incompletely Developed Meniscus possesses shorter shear length and thicker shear thickness than the prediction of Bretherton model and therefore is responsible for the more slippery regime. With an extended Bretherton model, we not only provide an analytical description to the IDM behavior but also the friction when the Capillary Number of the moving droplet is larger than the Critical Capillary Number.


Superconductivity from spin fluctuations and long-range interactions in magic-angle twisted bilayer graphene. (arXiv:2309.02178v1 [cond-mat.mes-hall])
Lauro B. Braz, George B. Martins, Luis G.G.V. Dias da Silva

Magic-angle twisted bilayer graphene (MATBG) has been extensively explored both theoretically and experimentally as a suitable platform for a rich and tunable phase diagram that includes ferromagnetism, charge order, broken symmetries, and unconventional superconductivity. In this work, we investigate the intricate interplay between long-range electron-electron interactions, spin fluctuations, and superconductivity in MATBG. By employing a low-energy model for MATBG that captures the correct shape of the flat bands, we explore the effects of short- and long-range interactions on spin fluctuations and their impact on the superconducting (SC) pairing vertex in the Random Phase Approximation (RPA). We find that the SC state is notably influenced by the strength of long-range Coulomb interactions. Interestingly, our RPA calculations indicate that there is a regime where the system can traverse from a magnetic phase to the SC phase by \emph{increasing} the relative strength of long-range interactions compared to the on-site ones. These findings underscore the relevance of electron-electron interactions in shaping the intriguing properties of MATBG and offer a pathway for designing and controlling its SC phase.


On the origin of circular dichroism in angular resolved photoemission from graphene, graphite, and WSe$_2$ family of materials. (arXiv:2309.02187v1 [cond-mat.mtrl-sci])
Lukasz Plucinski

Circular dichroism in angle-resolved photoemission (CD-ARPES) is one of the promising techniques for obtaining experimental insight into topological properties of novel materials, in particular to the orbital angular momentum (OAM) in dispersive bands, which might be related, albeit certainly in a non-trivial way, to the momentum resolved Berry curvature of the bands. Therefore, it is important to understand how non-vanishing CD-ARPES signal arises in graphene, a material where Dirac bands are made from C $|2p_z\rangle$ orbitals that carry zero OAM, spin-orbit-coupling (SOC) can be neglected, and Berry curvature effectively vanishes. Dubs et al., Phys. Rev. B 32, 8389 (1985) have demonstrated non-vanishing cricular dichroism in angular distribution (CDAD) from an oriented $p_z$ orbital, and this process can be responsible for the experimentally observed CD-ARPES in graphene. In this paper, we derive the CD-ARPES from $p_z$ orbitals by elementary means, using only simple algebraic formulas and tabulated numerical values, and show that it leads to significant CD-ARPES signal over the entire vacuum ultraviolet and soft x-ray energy range, with an exception of the photon energy region near $h\nu \approx 40$ eV. We also demonstrate that another process, emerging from the finite electron inelastic mean free path, also leads to CD-ARPES of the potentially similar order of magnitude, as previously discussed by Moser, J. Electron Spectrosc. Relat. Phenom. 214, 29 (2017). We present calculated CDAD maps for selected orbitals and briefly discuss the consequences of the findings for CD-ARPES, focusing on graphene, graphite and WSe$_2$.


Space charge and screening of a supercritical impurity cluster in monolayer graphene. (arXiv:2309.02199v1 [cond-mat.mes-hall])
Eugene B. Kolomeisky, Joseph P. Straley

Coulomb impurity of charge $Ze$ is known to destabilize the ground state of undoped graphene with respect to creation of screening space charge if $Z$ exceeds a critical value of $1/2\alpha$ set by material's fine structure constant $\alpha$. Recent experimental advances made it possible to explore this transition in a controlled manner by tuning $Z$ across the critical point. Combined with relatively large value of $\alpha$ this opens a possibility to study graphene's screening response to a supercritical impurity $Z\alpha\gg1$ when the screening charge is large, and the Thomas-Fermi analysis, that we revisit, is adequate. The character of screening in this regime is controlled by the dimensionless screening parameter $Z\alpha^{2}$. Specifically, for circular impurity cluster most of the screening charge in the weak-screening regime $Z\alpha^{2}\ll1$ is found to reside outside the cluster. The strong-screening regime $Z\alpha^{2}\gg1$ provides a realization of the Thomson atom: most of the screening charge is inside the cluster nearly perfectly neutralizing the source charge with the exception of a transition layer near cluster's edge where the rest of the space charge is localized.


Unveiling the electronic properties of BiP$_3$ triphosphide from bulk to heterostructures by first principles calculations. (arXiv:2309.02216v1 [cond-mat.mtrl-sci])
Dominike P. de Andrade Deus, Igor S. S. de Oliveira, Roberto Hiroki Miwa, Erika L. Nascimento

Triphosphides, with a chemical formula of XP$_3$ (X is a group IIIA, IVA, or VA element), have recently attracted much attention due to their great potential in several applications. Here, using density functional theory calculations, we describe for the first time the structural and electronic properties of the bulk bismuth triphosphide (BiP$_3$). Phonon spectra and molecular dynamics simulations confirm that the 3D crystal of BiP$_3$ is a metal thermodynamically stable with no bandgap. Unlike the bulk, the mono-, bi-, tri-, and tetra-layers of BiP$_3$ are semiconductors with a bandgap ranging from 1.4 to 0.06 eV. However, stackings with more than five layers exhibit metallic behavior equal to the bulk. The results show that quantum confinement is a powerful tool for tuning the electronic properties of BiP$_3$ triphosphide, making it suitable for technological applications. Building on this, the electronic properties of van der Waals heterostructure constructed by graphene (G) and the \bip~monolayer (m-\bip) were investigated. Our results show that the Dirac cone in graphene remains intact in this heterostructure. At the equilibrium interlayer distance, the G/m-BiP$_3$ forms an n-type contact with a Schottky barrier height of 0.5 eV. It is worth noting that the SHB in the G/m-BiP$_3$ heterostructure can be adjusted by changing the interlayer distance or applying a transverse electric field. Thus, we show that few-layers \bip~is an interesting material for realizing nanoelectronic and optoelectronic devices and is an excellent option for designing Schottky nanoelectronic devices.


Magnetic and structural properties of the iron silicide superconductor LaFeSiH. (arXiv:2309.02241v1 [cond-mat.supr-con])
M. F. Hansen, S. Layek, J.-B. Vaney, L. Chaix, M. R. Suchomel, M. Mikolasek, G. Garbarino, A. Chumakov, R. Rüffer, V. Nassif, T. Hansen, E. Elkaim, T. Pelletier, H. Mayaffre, F. Bernardini, A. Sulpice, M. Núñez-Regueiro, P. Rodière, A. Cano, S. Tencé, P. Toulemonde, M.-H. Julien, M. d'Astuto

The magnetic and structural properties of the recently discovered pnictogen/chalcogen-free superconductor LaFeSiH ($T_c\simeq10$~K) have been investigated by $^{57}$Fe synchrotron M{\"o}ssbauer source (SMS) spectroscopy, x-ray and neutron powder diffraction and $^{29}$Si nuclear magnetic resonance spectroscopy (NMR). No sign of long range magnetic order or local moments has been detected in any of the measurements and LaFeSiH remains tetragonal down to 2 K. The activated temperature dependence of both the NMR Knight shift and the relaxation rate $1/T_1$ is analogous to that observed in strongly overdoped Fe-based superconductors. These results, together with the temperature-independent NMR linewidth, show that LaFeSiH is an homogeneous metal, far from any magnetic or nematic instability, and with similar Fermi surface properties as strongly overdoped iron pnictides. This raises the prospect of enhancing the $T_c$ of LaFeSiH by reducing its carrier concentration through appropriate chemical substitutions. Additional SMS spectroscopy measurements under hydrostatic pressure up to 18.8~GPa found no measurable hyperfine field.


Controlling Spontaneous Orientation Polarization in Organic Semiconductors -- The Case of Phosphine Oxides. (arXiv:2309.02261v1 [cond-mat.mtrl-sci])
Albin Cakaj, Markus Schmid, Alexander Hofmann, Wolfgang Brütting

Upon film growth by physical vapor deposition, the preferential orientation of polar organic molecules can result in a non-zero permanent dipole moment (PDM) alignment, causing a macroscopic film polarization. This effect, known as spontaneous orientation polarization (SOP), was studied in the case of different phosphine oxides. We investigate the control of SOP by molecular design and film-growth conditions. Our results show that using less polar phosphine oxides with just one phosphor-oxygen bond yields an exceptionally high degree of SOP with the so-called giant surface potential (slope) reaching more than 150mV/nm in a neat BCPO film grown at room temperature. Additionally, by altering the evaporation rate and the substrate temperature, we are able to control the SOP magnitude over a broad range from 0 to almost 300mV/nm. Diluting BCPO in a non-polar host enhances the PDM alignment only marginally, but combining temperature control together with dipolar doping can result in almost perfectly aligned molecules with more than 80% of their PDMs standing upright on the substrate on average.


Probing defect induced room temperature ferromagnetism in CVD grown MoO3 flakes: A correlation with electronic structure and first principle-based calculations. (arXiv:2309.02277v1 [cond-mat.mtrl-sci])
Sharmistha Dey, Vikash Mishra, Neetesh Dhakar, Sunil Kumar, Pankaj Srivastava, Santanu Ghosh

In this paper, we report the growth of pure {\alpha}-MoO3 micro-flakes by CVD technique and their structural, electronic, optical, and magnetic properties. Samples are annealed at various temperatures in an H2 atmosphere to induce ferromagnetism. All the samples exhibit ferromagnetism at room temperature, and 250oC annealed sample shows the highest magnetic moment of 0.087 emu/g. It is evident from PL data that pristine as well as annealed samples contain different types of defects like oxygen vacancies, surface defects, interstitial oxygen, etc. It is deduced from the analysis of Mo3d and O1s core-level XPS spectra that oxygen vacancies increase up to an annealing temperature of 250oC that correlates with the magnetic moment. Significant changes in the total density of states and also in the magnetic moment for two and three oxygen vacancies are noticed through first-principle-based calculations. It is concluded that the magnetic moment is produced by oxygen vacancies or vacancy clusters, which is consistent with our experimental findings.


Inferring effective couplings with Restricted Boltzmann Machines. (arXiv:2309.02292v1 [cond-mat.dis-nn])
Aurélien Decelle, Cyril Furtlehner, Alfonso De Jesus Navas Gómez, Beatriz Seoane

Generative models offer a direct way to model complex data. Among them, energy-based models provide us with a neural network model that aims to accurately reproduce all statistical correlations observed in the data at the level of the Boltzmann weight of the model. However, one challenge is to understand the physical interpretation of such models. In this study, we propose a simple solution by implementing a direct mapping between the energy function of the Restricted Boltzmann Machine and an effective Ising spin Hamiltonian that includes high-order interactions between spins. This mapping includes interactions of all possible orders, going beyond the conventional pairwise interactions typically considered in the inverse Ising approach, and allowing the description of complex datasets. Earlier work attempted to achieve this goal, but the proposed mappings did not do properly treat the complexity of the problem or did not contain direct prescriptions for practical application. To validate our method, we perform several controlled numerical experiments where the training samples are equilibrium samples of predefined models containing local external fields, two-body and three-body interactions in various low-dimensional topologies. The results demonstrate the effectiveness of our proposed approach in learning the correct interaction network and pave the way for its application in modeling interesting datasets. We also evaluate the quality of the inferred model based on different training methods.


Probing the Dark Exciton in Monolayer MoS$_2$ by Quantum Interference in Second Harmonic Generation Spectroscopy. (arXiv:2309.02303v1 [cond-mat.mes-hall])
Chenjiang Qian, Viviana Villafañe, Pedro Soubelet, Peirui Ji, Andreas V. Stier, Jonathan J. Finley

We report resonant second harmonic generation (SHG) spectroscopy of an hBN-encapsulated monolayer of MoS$_2$. By tuning the energy of the excitation laser, we identify a dark state transition (D) that is blue detuned by +25 meV from the neutral exciton X$^0$. We observe a splitting of the SHG spectrum into two distinct peaks and a clear anticrossing between them as the SHG resonance is tuned through the energy of the dark exciton D. This observation is indicative of quantum interference arising from the strong two-photon light-matter interaction. We further probe the incoherent relaxation from the dark state to the bright excitons, including X$^0$ and localized excitons LX, by the resonant enhancement of their intensities at the SHG-D resonance. The relaxation of D to bright excitons is strongly suppressed on the bare substrate whilst enabled when the hBN/MoS$_2$/hBN heterostructure is integrated in a nanobeam cavity. The relaxation enabled by the cavity is explained by the phonon scattering enhanced by the cavity phononic effects. Our work reveals the two-photon quantum interference with long-lived dark states and enables the control through nanostructuring of the substrate. These results indicate the great potential of dark excitons in 2D-material based nonlinear quantum devices.


Hidden subsystem symmetry protected states in competing topological orders. (arXiv:2309.02307v1 [cond-mat.str-el])
Shi Feng

We reveal the connection between two-dimensional subsystem symmetry-protected topological (SSPT) states and two-dimensional topological orders via a self-dual frustrated toric code model. This model, an enrichment of the toric code (TC) with its dual interactions, can be mapped to a model defined on the dual lattice with subsystem symmetries and subextensive ground state degeneracy. The map connects exactly the frustrated TC to two copies of the topological plaquette Ising model (TPIM), as a strong SSPT model with linear subsystem symmetries. The membrane order parameter of TPIM is exactly mapped to dual TC stabilizers as the order parameter of the frustrated TC model, and the transition between the SSPT-ordered TPIM to the trivial paramagnetic phase is mapped to the transition between two distinct topological orders. We also demonstrate that this picture of frustrated TC can be used to construct other SSPT models, hinting at a subtle linkage between SSPT order and topological order in two dimensions.


Landau Theory of Barocaloric Plastic Crystals. (arXiv:2309.02316v1 [cond-mat.mtrl-sci])
Marín-Delgado R., Moya, X., Guzmán-Verri, G. G

We present a simple Landau phenomenology for plastic-to-crystal phase transitions and use the resulting model to calculate barocaloric effects in plastic crystals that are driven by hydrostatic pressure. The essential ingredients of the model are (i) a multipole-moment order parameter that describes the orientational ordering of the constituent molecules, (ii) coupling between such order parameter and elastic strains, and (iii) the thermal expansion of the solid. The model captures main features of plastic-to-crystal phase transitions, namely large volume and entropy changes at the transition, and strong dependence of the transition temperature with pressure. Using solid C$_{60}$ under $0.60\,$GPa as case example, we show that calculated peak isothermal entropy changes of $\sim 58 \,{\rm J K^{-1} kg^{-1}}$ and peak adiabatic entropy changes of $\sim 23 \,{\rm K}$ agree well with experimental values.


Electrically Driven Spin Resonance of 4f Electrons in a Single Atom on a Surface. (arXiv:2309.02348v1 [cond-mat.mes-hall])
Stefano Reale, Jiyoon Hwang, Jeongmin Oh, Harald Brune, Andreas J. Heinrich, Fabio Donati, Yujeong Bae

A pivotal challenge in present quantum technologies lies in reconciling long coherence times with efficient manipulation of the quantum states of a system. Lanthanide atoms, with their well-localized 4f electrons, emerge as a promising solution to this dilemma if provided with a rational design of the manipulation and detection schemes. Here we utilize a scanning tunneling microscope to construct tailored spin structures and perform electron spin resonance on a single lanthanide atom in such a structure. A magnetically coupled structure made of an Erbium and a Titanium atom at sub-nanometer distance enables us to both drive Erbium's 4f electron spins and indirectly probe them through the Titanium's 3d electrons. In this coupled configuration, the Erbium spin states exhibit a four-fold increase in the spin relaxation time and a two-fold increase in the driving efficiency compared to the 3d electron counterparts. Our work provides a new approach to accessing highly protected spin states, enabling us to control them in an all-electric fashion.


Induced Monolayer Altermagnetism in MnP(S,Se)$_3$ and FeSe. (arXiv:2309.02355v1 [cond-mat.mes-hall])
Igor Mazin, Rafael González-Hernández, Libor Šmejkal

Altermagnets (AM) are a recently discovered third class of collinear magnets, distinctly different from conventional ferromagnets (FM) and antiferromagnets (AF). AM have been actively researched in the last few years, but two aspects so far remain unaddressed: (1) Are there realistic 2D single-layer altermagnets? And (2) is it possible to functionalize a conventional AF into AM by external stimuli? In this paper we address both issues by demonstrating how a well-known 2D AF, MnP(S,Se)$_3$ can be functionalized into strong AM by applying out-of-plane electric field. Of particular interest is that the induced altermagnetism is of a higher even-parity wave symmetry than expected in 3D AM with similar crystal symmetries. We confirm our finding by first-principles calculations of the electronic structure and magnetooptical response. We also propose that recent observations of the time-reversal symmetry breaking in the famous Fe-based superconducting chalchogenides, either in monolayer form or in the surface layer, may be related not to an FM, as previously assumed, but to the induced 2D AM order. Finally, we show that monolayer FeSe can simultaneously exhibit unconventional altermagnetic time-reversal symmetry breaking and quantized spin Hall conductivity indicating possibility to research an intriquing interplay of 2D altermagnetism with topological and superconducting states within a common crystal-potential environment.


Predictions and Uncertainty Estimates of Reactor Pressure Vessel Steel Embrittlement Using Machine Learning. (arXiv:2309.02362v1 [cond-mat.mtrl-sci])
Ryan Jacobs, Takuya Yamamoto, G. Robert Odette, Dane Morgan

An essential aspect of extending safe operation of the active nuclear reactors is understanding and predicting the embrittlement that occurs in the steels that make up the Reactor pressure vessel (RPV). In this work we integrate state of the art machine learning methods using ensembles of neural networks with unprecedented data collection and integration to develop a new model for RPV steel embrittlement. The new model has multiple improvements over previous machine learning and hand-tuned efforts, including greater accuracy (e.g., at high-fluence relevant for extending the life of present reactors), wider domain of applicability (e.g., including a wide-range of compositions), uncertainty quantification, and online accessibility for easy use by the community. These improvements provide a model with significant new capabilities, including the ability to easily and accurately explore compositions, flux, and fluence effects on RPV steel embrittlement for the first time. Furthermore, our detailed comparisons show our approach improves on the leading American Society for Testing and Materials (ASTM) E900-15 standard model for RPV embrittlement on every metric we assessed, demonstrating the efficacy of machine learning approaches for this type of highly demanding materials property prediction.


Phononic drumhead surface state in distorted kagome compound RhPb. (arXiv:2309.02419v1 [cond-mat.mtrl-sci])
Andrzej Ptok, William R. Meier, Aksel Kobiałka, Surajit Basak, Małgorzata Sternik, Jan Łażewski, Paweł T. Jochym, Michael A. McGuire, Brian C. Sales, Hu Miao, Przemysław Piekarz, Andrzej M. Oleś

RhPb was initially recognized as one of a CoSn-like compounds with $P6/mmm$ symmetry, containing an ideal kagome lattice of $d$-block atoms. However, theoretical calculations predict the realization of the phonon soft mode which leads to the kagome lattice distortion and stabilization of the structure with $P\bar{6}2m$ symmetry [A. Ptok et al., Phys. Rev. B 104, 054305 (2021)]. Here, we present the single crystal x-ray diffraction results supporting this prediction. Furthermore, we discuss the main dynamical properties of RhPb with $P\bar{6}2m$ symmetry. The bulk phononic dispersion curves contain several flattened bands, Dirac nodal lines, and triple degenerate Dirac points. As a consequence, the phononic drumhead surface state is realized for the (100) surface, terminated by the zigzag-like edge of Pb honeycomb sublattice.


Anomalous sound attenuation in Weyl semimetals in magnetic and pseudomagnetic fields. (arXiv:2102.04510v3 [cond-mat.mes-hall] UPDATED)
P. O. Sukhachov, L. I. Glazman

We evaluate the sound attenuation in a Weyl semimetal subject to a magnetic field or a pseudomagnetic field associated with a strain. Due to the interplay of intra- and inter-node scattering processes as well as screening, the fields generically reduce the sound absorption. A nontrivial dependence on the relative direction of the magnetic field and the sound wave vector, i.e., the magnetic sound dichroism, can occur in materials with nonsymmetric Weyl nodes (e.g., different Fermi velocities and/or relaxation times). It is found that the sound dichroism in Weyl materials can also be activated by an external strain-induced pseudomagnetic field. In view of the dependence on the field direction, the dichroism may lead to a weak enhancement of the sound attenuation compared with its value at vanishing fields.


Dynamical quantum ergodicity from energy level statistics. (arXiv:2205.05704v3 [quant-ph] UPDATED)
Amit Vikram, Victor Galitski

Ergodic theory provides a rigorous mathematical description of chaos in classical dynamical systems, including a formal definition of the ergodic hierarchy. How ergodic dynamics is reflected in the energy levels and eigenstates of a quantum system is the central question of quantum chaos, but a rigorous quantum notion of ergodicity remains elusive. Closely related to the classical ergodic hierarchy is a less-known notion of cyclic approximate periodic transformations [see, e.g., I. Cornfield, S. Fomin, and Y. Sinai, Ergodic Theory (Springer-Verlag New York, 1982)], which maps any "ergodic" dynamical system to a cyclic permutation on a circle and arguably represents the most elementary form of ergodicity. This paper shows that cyclic ergodicity generalizes to quantum dynamical systems, and provides a rigorous observable-independent definition of quantum ergodicity. It implies the ability to construct an orthonormal basis, where quantum dynamics transports any initial basis vector to have a sufficiently large overlap with each of the other basis vectors in a cyclic sequence. It is proven that the basis, maximizing the overlap over all such quantum cyclic permutations, is obtained via the discrete Fourier transform of the energy eigenstates. This relates quantum cyclic ergodicity to energy level statistics. The level statistics of Wigner-Dyson random matrices, usually associated with quantum chaos on empirical grounds, is derived as a special case of this general relation. To demonstrate generality, we prove that irrational flows on a 2D torus are classical and quantum cyclic ergodic, with spectral rigidity distinct from Wigner-Dyson. Finally, we motivate a quantum ergodic hierarchy of operators and discuss connections to eigenstate thermalization. This work provides a general framework for transplanting some rigorous concepts of ergodic theory to quantum dynamical systems.


Restoration of the non-Hermitian bulk-boundary correspondence via topological amplification. (arXiv:2207.12427v4 [quant-ph] UPDATED)
Matteo Brunelli, Clara C. Wanjura, Andreas Nunnenkamp

Non-Hermitian (NH) lattice Hamiltonians display a unique kind of energy gap and extreme sensitivity to boundary conditions. Due to the NH skin effect, the separation between edge and bulk states is blurred and the (conventional) bulk-boundary correspondence is lost. Here, we restore the bulk-boundary correspondence for the most paradigmatic class of NH Hamiltonians, namely those with one complex band and without symmetries. We obtain the desired NH Hamiltonian from the (mean-field) unconditional evolution of driven-dissipative cavity arrays, in which NH terms -- in the form of non-reciprocal hopping amplitudes, gain and loss -- are explicitly modeled via coupling to (engineered and non-engineered) reservoirs. This approach removes the arbitrariness in the definition of the topological invariant, as point-gapped spectra differing by a complex-energy shift are not treated as equivalent; the origin of the complex plane provides a common reference (base point) for the evaluation of the topological invariant. This implies that topologically non-trivial Hamiltonians are only a strict subset of those with a point gap and that the NH skin effect does not have a topological origin. We analyze the NH Hamiltonians so obtained via the singular value decomposition, which allows to express the NH bulk-boundary correspondence in the following simple form: an integer value $\nu$ of the topological invariant defined in the bulk corresponds to $\vert \nu\vert$ singular vectors exponentially localized at the system edge under open boundary conditions, in which the sign of $\nu$ determines which edge. Non-trivial topology manifests as directional amplification of a coherent input with gain exponential in system size. Our work solves an outstanding problem in the theory of NH topological phases and opens up new avenues in topological photonics.


Topological Matter and Fractional Entangled Quantum Geometry through Light. (arXiv:2209.15381v5 [cond-mat.mes-hall] UPDATED)
Karyn Le Hur

Here, we reveal our recent progress on a geometrical approach of quantum physics and topological crystals linking with Dirac magnetic monopoles and gauge fields through classical electrodynamics. The Bloch sphere of a quantum spin-1/2 particle acquires an integer topological charge in the presence of a radial magnetic field. We show that global topological properties are encoded from the poles of the surface allowing a correspondence between smooth fields, metric and quantum distance with the square of the topological number. The information is transported from each pole to the equatorial plane on a thin Dirac string. We develop the theory, "quantum topometry" in space and time, and present applications on transport from a Newtonian approach, on a quantized photo-electric effect from circular dichroism of light towards topological band structures of crystals. Edge modes related to topological lattice models are resolved analytically when deforming the sphere or ellipse onto a cylinder. Topological properties of the quantum Hall effect, quantum anomalous Hall effect and quantum spin Hall effect on the honeycomb lattice can be measured locally in the Brillouin zone from light-matter coupling. The formalism allows us to include interaction effects from the momentum space. Interactions may also result in fractional entangled geometry within the curved space. We develop a relation between entangled wavefunction in quantum mechanics, coherent superposition of geometries, a way to one-half topological numbers and Majorana fermions. We show realizations in topological matter. We present a link between axion electrodynamics, topological insulators on a surface of a cube and the two-spheres' model via merons.


1/4 is the new 1/2 when topology is intertwined with Mottness. (arXiv:2210.11486v5 [cond-mat.mes-hall] UPDATED)
Peizhi Mai, Jinchao Zhao, Benjamin E. Feldman, Philip W. Phillips

In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin susceptibility is consistent with a possible ferromagnetic state at $T=0$. The onset of such magnetism would convert the quantum spin Hall to a quantum anomalous Hall effect. While such a symmetry-broken phase typically is accompanied by a gap, we find that the interaction strength must exceed a critical value for this to occur. Hence, we predict that topology can obtain in a gapless phase but only in the presence of interactions in dispersive bands. These results explain the recent quarter-filled quantum anomalous Hall effects seen in moire systems.


New type of helical topological superconducting pairing at finite excitation energies. (arXiv:2210.11955v3 [cond-mat.mes-hall] UPDATED)
Masoud Bahari, Song-Bo Zhang, Chang-An Li, Sang-Jun Choi, Carsten Timm, Björn Trauzettel

We propose a new type of helical topological superconductivity away from the Fermi surface in three-dimensional time-reversal-symmetric odd-parity multiband superconductors. In these systems, pairing between electrons originating from different bands is responsible for the corresponding topological phase transition. Consequently, a pair of helical topological Dirac surface states emerges at finite excitation energies. These helical Dirac surface states are tunable in energy by chemical potential and strength of band-splitting. They are protected by pseudospin rotation symmetry. We suggest concrete materials in which this phenomenon could be observed.


Emergent Symmetry in Quantum Phase Transitions: From Deconfined Quantum Critical Point to Gapless Quantum Spin Liquid. (arXiv:2212.00707v2 [cond-mat.str-el] UPDATED)
Wen-Yuan Liu, Shou-Shu Gong, Wei-Qiang Chen, Zheng-Cheng Gu

The emergence of exotic quantum phenomena in frustrated magnets is rapidly driving the development of quantum many-body physics, raising fundamental questions on the nature of quantum phase transitions. Here we unveil the behaviour of emergent symmetry involving two extraordinarily representative phenomena, i.e., the deconfined quantum critical point (DQCP) and the quantum spin liquid (QSL) state. Via large-scale tensor network simulations, we study a spatially anisotropic spin-1/2 square-lattice frustrated antiferromagnetic (AFM) model, namely the $J_{1x}$-$J_{1y}$-$J_2$ model, which contains anisotropic nearest-neighbor couplings $J_{1x}$, $J_{1y}$ and the next nearest neighbor coupling $J_2$. For small $J_{1y}/J_{1x}$, by tuning $J_2$, a direct continuous transition between the AFM and valence bond solid phase is observed.(Of course, the possibility of weakly first order transition can not be fully excluded.) With growing $J_{1y}/J_{1x}$, a gapless QSL phase gradually emerges between the AFM and VBS phases. We observe an emergent O(4) symmetry along the AFM--VBS transition line, which is consistent with the prediction of DQCP theory. Most surprisingly, we find that such an emergent O(4) symmetry holds for the whole QSL--VBS transition line as well. These findings reveal the intrinsic relationship between the QSL and DQCP from categorical symmetry point of view, and strongly constrain the quantum field theory description of the QSL phase. The phase diagram and critical exponents presented in this paper are of direct relevance to future experiments on frustrated magnets and cold atom systems.


Higher-order topological superconductivity in a topological metal 1T$^\prime$-MoTe$_2$. (arXiv:2212.06197v3 [cond-mat.supr-con] UPDATED)
Sheng-Jie Huang, Kyungwha Park, Yi-Ting Hsu

One key challenge in the field of topological superconductivity (Tsc) has been the rareness of material realization. This is true not only for the first-order Tsc featuring Majorana surface modes, but also for the higher-order Tsc, which host Majorana hinge and corner modes. Here, we propose a four-step strategy that mathematically derives comprehensive guiding principles for the search and design for materials of general higher-order Tsc phases. Specifically, such recipes consist of conditions on the normal state and pairing symmetry that can lead to a given higher-order Tsc state. We demonstrate this strategy by obtaining recipes for achieving three-dimensional higher-order Tsc phases protected by the inversion symmetry. Following our recipe, we predict that the observed superconductivity in centrosymmetric MoTe$_2$ is a candidate for higher-order Tsc with corner modes. Our proposed strategy enables systematic materials search and design for higher-order Tsc, which can mobilize the experimental efforts and accelerate the material discovery for higher-order Tsc phases.


Thermodynamic efficiency of atmospheric motion governed by Lorenz system. (arXiv:2302.03887v3 [nlin.CD] UPDATED)
Zhen Li, Yuki Izumida

The Lorenz system was derived on the basis of a model of convective atmospheric motions and may serve as a paradigmatic model for considering a complex climate system. In this study, we formulated the thermodynamic efficiency of convective atmospheric motions governed by the Lorenz system by treating it as a non-equilibrium thermodynamic system. Based on the fluid conservation equations under the Oberbeck-Boussinesq approximation,the work necessary to maintain atmospheric motion and heat fluxes at the boundaries were calculated. Using these calculations, the thermodynamic efficiency was formulated for stationary and chaotic dynamics. The numerical results show that, for both stationary and chaotic dynamics, the efficiency tends to increase as the atmospheric motion is driven out of thermodynamic equilibrium when the Rayleigh number increases. However, it is shown that the efficiency is upper bounded by the maximum efficiency, which is expressed in terms of the parameters characterizing the fluid and the convective system. The analysis of the entropy generation rate was also performed for elucidating the difference between the thermodynamic efficiency of conventional heat engines and the present atmospheric heat engine. It is also found that there exists an abrupt drop in efficiency at the critical Hopf bifurcation point, where the dynamics change from stationary to chaotic. These properties are similar to those found previously in Malkus-Lorenz waterwheel system.


Stackings and effective models of bilayer dice lattices. (arXiv:2303.01452v2 [cond-mat.mes-hall] UPDATED)
P. O. Sukhachov, D. O. Oriekhov, E. V. Gorbar

We introduce and classify nonequivalent commensurate stackings for bilayer dice or $\mathcal{T}_3$ lattice. For each of the four stackings with vertical alignment of sites in two layers, a tight-binding model and an effective model describing the properties in the vicinity of the threefold band-crossing points are derived. Focusing on these band-crossing points, we found that although the energy spectrum remains always gapless, depending on the stacking, different types of quasiparticle spectra arise. They include those with flat, tilted, anisotropic semi-Dirac, and $C_3$-corrugated energy bands. We use the derived tight-binding models to calculate the density of states and the spectral function. The corresponding results reveal drastic redistribution of the spectral weight due to the inter-layer coupling that is unique for each of the stackings.


Observation of higher-order topological states on a quantum computer. (arXiv:2303.02179v2 [cond-mat.str-el] UPDATED)
Jin Ming Koh, Tommy Tai, Ching Hua Lee

Programmable quantum simulators such as superconducting quantum processors and ultracold atomic lattices represent rapidly developing emergent technology that may one day qualitatively outperform existing classical computers. Yet, apart from a few breakthroughs, the range of viable computational applications with current-day noisy intermediate-scale quantum (NISQ) devices is still significantly limited by gate errors, quantum decoherence, and the number of high-quality qubits. In this work, we develop an approach that places NISQ hardware as a particularly suitable platform for simulating multi-dimensional condensed matter systems, including lattices beyond three dimensions which are difficult to realize or probe in other settings. By fully exploiting the exponentially large Hilbert space of a quantum chain, we encoded a high-dimensional model in terms of non-local many-body interactions that can further be systematically transcribed into quantum gates. We demonstrate the power of our approach by realizing, on IBM transmon-based quantum computers, higher-order topological states in up to four dimensions, which are exotic phases that have never been realized in any quantum setting. With the aid of in-house circuit compression and error mitigation techniques, we measured the topological state dynamics and their protected mid-gap spectra to a high degree of accuracy, as benchmarked by reference exact diagonalization data. The time and memory needed with our approach scale favorably with system size and dimensionality compared to exact diagonalization on classical computers.


Floquet topological superconductors with many Majorana edge modes: topological invariants, entanglement spectrum and bulk-edge correspondence. (arXiv:2303.04674v3 [cond-mat.mes-hall] UPDATED)
Hailing Wu, Shenlin Wu, Longwen Zhou

One-dimensional Floquet topological superconductors possess two types of degenerate Majorana edge modes at zero and $\pi$ quasieneriges, leaving more room for the design of boundary time crystals and quantum computing schemes than their static counterparts. In this work, we discover Floquet superconducting phases with large topological invariants and arbitrarily many Majorana edge modes in periodically driven Kitaev chains. Topological winding numbers defined for the Floquet operator and Floquet entanglement Hamiltonian are found to generate consistent predictions about the phase diagram, bulk-edge correspondence and numbers of zero and $\pi$ Majorana edge modes of the system under different driving protocols. The bipartite entanglement entropy further show non-analytic behaviors around the topological transition point between different Floquet superconducting phases. These general features are demonstrated by investigating the Kitaev chain with periodically kicked pairing or hopping amplitudes. Our discovery reveals the rich topological phases and many Majorana edge modes that could be brought about by periodic driving fields in one-dimensional superconducting systems. It further introduces a unified description for a class of Floquet topological superconductors from their quasienergy bands and entanglement properties.


Optical conductivity of bilayer dice lattices. (arXiv:2303.08258v2 [cond-mat.mes-hall] UPDATED)
P. O. Sukhachov, D. O. Oriekhov, E. V. Gorbar

We calculate optical conductivity for bilayer dice lattices in commensurate vertically aligned stackings. The interband optical conductivity reveals a rich activation behavior unique for each of the four stackings. We found that the intermediate energy band, which corresponds to the flat band of a single-layer dice lattice, plays a different role for different stackings. The interband selection rules, which are crucial for the single-layer lattice, may become lifted in bilayer lattices. The results for effective and tight-binding models are found to be in qualitative agreement for some of the stackings and the reasons for the discrepancies for others are identified. Our findings propose optical conductivity as an effective tool to distinguish between different stackings in bilayer dice lattices.


PT breaking and RG flows between multicritical Yang-Lee fixed points. (arXiv:2304.08522v2 [cond-mat.stat-mech] UPDATED)
Máté Lencsés, Alessio Miscioscia, Giuseppe Mussardo, Gábor Takács

We study a novel class of Renormalization Group flows which connect multicritical versions of the two-dimensional Yang-Lee edge singularity described by the conformal minimal models M(2,2n+3). The absence in these models of an order parameter implies that the flows towards and between Lee-Yang edge singularities are all related to the spontaneous breaking of PT symmetry and comprise a pattern of flows in the space of PT symmetric theories consistent with the c-theorem and the counting of relevant directions. Additionally, we find that while in a part of the phase diagram the domains of unbroken and broken PT symmetry are separated by critical manifolds of class M(2,2n+3), other parts of the boundary between the two domains are not critical.


Confined states and topological phases in two-dimensional quasicrystalline $\pi$-flux model. (arXiv:2304.10699v2 [cond-mat.mes-hall] UPDATED)
Rasoul Ghadimi, Masahiro Hori, Takanori Sugimoto, Takami Tohyama

Motivated by topological equivalence between an extended Haldane model and a chiral-$\pi$-flux model on a square lattice, we apply $\pi$-flux models to two-dimensional bipartite quasicrystals with rhombus tiles in order to investigate topological properties in aperiodic systems. Topologically trivial $\pi$-flux models in the Ammann-Beenker tiling lead to massively degenerate confined states whose energies and fractions differ from the zero-flux model. This is different from the $\pi$-flux models in the Penrose tiling, where confined states only appear at the center of the bands as is the case of a zero-flux model. Additionally, Dirac cones appear in a certain $\pi$-flux model of the Ammann-Beenker approximant, which remains even if the size of the approximant increases. Nontrivial topological states with nonzero Bott index are found when staggered tile-dependent hoppings are introduced in the $\pi$-flux models. This finding suggests a new direction in realizing nontrivial topological states without a uniform magnetic field in aperiodic systems.


Fast dynamics and high effective dimensionality of liquid fluidity. (arXiv:2304.11909v3 [cond-mat.stat-mech] UPDATED)
Cillian Cockrell, Oliver Dicks, Ilian T. Todorov, Alin M. Elena, Kostya Trachenko

Fluidity, the ability of liquids to flow, is the key property distinguishing liquids from solids. This fluidity is set by the mobile transit atoms moving from one quasi-equilibrium point to the next. The nature of this transit motion is unknown. Here, we show that flow-enabling transits form a dynamically distinct sub-ensemble where atoms move on average faster than the overall system, with a manifestly non-Maxwellian velocity distribution. This is in contrast to solids and gases where no distinction of different ensembles can be made and where the distribution is always Maxwellian. The non-Maxwellian distribution is described by an exponent $\alpha$ corresponding to high dimensionality of space. This is generally similar to extra synthetic dimensions in topological quantum matter, albeit higher dimensionality in liquids is not integer but is fractional. The dimensionality is close to 4 at melting and exceeds 4 at high temperature. $\alpha$ has a maximum as a function of temperature and pressure in liquid and supercritical states, returning to its Maxwell value in the solid and gas states.


Quantum phase transition between symmetry enriched topological phases in tensor-network states. (arXiv:2305.02432v2 [cond-mat.str-el] UPDATED)
Lukas Haller, Wen-Tao Xu, Yu-Jie Liu, Frank Pollmann

Quantum phase transitions between different topologically ordered phases exhibit rich structures and are generically challenging to study in microscopic lattice models. In this work, we propose a tensor-network solvable model that allows us to tune between different symmetry enriched topological (SET) phases. Concretely, we consider a decorated two-dimensional toric code model for which the ground state can be expressed as a two-dimensional tensor-network state with bond dimension $D=3$ and two tunable parameters. We find that the time-reversal (TR) symmetric system exhibits three distinct phases (i) an SET toric code phase in which anyons transform non-trivially under TR, (ii) a toric code phase in which TR does not fractionalize, and (iii) a topologically trivial phase that is adiabatically connected to a product state. We characterize the different phases using the topological entanglement entropy and a membrane order parameter that distinguishes the two SET phases. Along the phase boundary between the SET toric code phase and the toric code phase, the model has an enhanced $U(1)$ symmetry and the ground state is a quantum critical loop gas wavefunction whose squared norm is equivalent to the partition function of the classical $O(2)$ model. By duality transformations, this tensor-network solvable model can also be used to describe transitions between SET double-semion phases and between $\mathbb{Z}_2\times\mathbb{Z}_2^T$ symmetry protected topological phases in two dimensions.


On the validity of the bipolaron model for PEDOT, with and without AlCl4- anions. (arXiv:2305.11720v2 [cond-mat.mtrl-sci] UPDATED)
Ben Craig, Peter Townsend, Chris Kriton-Skylaris, Carlos Ponce de Leon, Denis Kramer

The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most researched materials. The 1980s bipolaron model remains the dominant interpretation of the electronic structure of PEDOT. Recent theoretical studies have provided updated definitions of key concepts such as bipolarons or polaron pairs, but these have not yet become widely known. In this work, we use density functional theory to investigate the electronic structure of PEDOT oligomers, with and without co-located AlCl4- anions. By considering the influence of oligomer length, oxidation or anion concentration and spin state, we find no evidence for self-localisation of positive charges in PEDOT as predicted by the bipolaron model at the hybrid functional level. Our results show distortions that exhibit either a single or a double peak in bond length alternations and charge density. Either can occur at any oxidation or anion concentration. We note that other distortion shapes are also possible. Rather than representing bipolarons or polaron pairs in the original model, these are electron distributions driven by a range of factors. Localisation of distortions does occur with anions, and distortions can span an arbitrary number of nearby anions. Conductivity in conducting polymers has been observed to reduce at anion concentrations above 0.5. We show at high anion concentrations, the energy of the localised, non-bonding anionic orbitals approaches that of the system HOMO due to Coulombic repulsion between anions. We hypothesize that with nucleic motion in the macropolymer, these orbitals will interfere with the hopping of charge carriers between sites of similar energy, lowering conductivity.


Candidate local parent Hamiltonian for 3/7 fractional quantum Hall effect. (arXiv:2305.12400v2 [cond-mat.str-el] UPDATED)
Koji Kudo, A. Sharma, G. J. Sreejith, J. K. Jain

While a parent Hamiltonian for Laughlin $1/3$ wave function has been long known in terms of the Haldane pseudopotentials, no parent Hamiltonians are known for the lowest-Landau-level projected wave functions of the composite fermion theory at $n/(2n+1)$ with $n\geq2$. If one takes the two lowest Landau levels to be degenerate, the Trugman-Kivelson interaction produces the unprojected 2/5 wave function as the unique zero energy solution. If the lowest three Landau levels are assumed to be degenerate, the Trugman-Kivelson interaction produces a large number of zero energy states at $\nu=3/7$. We propose that adding an appropriately constructed three-body interaction yields the unprojected $3/7$ wave function as the unique zero energy solution, and report extensive exact diagonalization studies that provide strong support to this proposal.


Scaling theory of intrinsic Kondo and Hund's rule interactions in magic-angle twisted bilayer graphene. (arXiv:2306.03121v2 [cond-mat.str-el] UPDATED)
Yang-Zhi Chou, Sankar Das Sarma

Motivated by the recent studies of intrinsic local moments and Kondo-driven phases in magic-angle twisted bilayer graphene, we investigate the renormalization of Kondo coupling ($J_K$) and the competing Hund's rule interaction ($J$) in the low-energy limit. Specifically, we consider a surrogate single-impurity generalized Kondo model and employ the poor man's scaling approach. The scale-dependent $J_K$ and $J$ are derived analytically within the one-loop poor man's scaling approach, and the Kondo temperature ($T_K$) and the characteristic Hund's rule coupling ($J^*$, defined by the renormalized value of $J$ at some small finite energy scale) are estimated over a wide range of filling factors. We find that $T_K$ depends strongly on the filling factors as well as the value of $J_K$. Slightly doping away from integer fillings and/or increasing $J_K$ may substantially enhance $T_K$ in the parameter regime relevant to experiments. $J^*$ is always reduced from the bare value of $J$, but the filling factor dependence is not as significant as it is for $T_K$. Our results suggest that it is essential to incorporate the renormalization of $J_K$ and $J$ in the many-body calculations, and Kondo screening should occur for a wide range of fractional fillings in magic-angle twisted bilayer graphene, implying the existence of Kondo-driven correlated metallic phases. We also point out that the observation of distinct phases at integer fillings in different samples may be due to the variation of $J_K$ in addition to disorder and strain in the experiments.


From Edge State Physics to Entanglement Spectrum: Studying Interactions and Impurities in Two-Dimensional Topological Insulators. (arXiv:2307.01913v2 [cond-mat.mes-hall] UPDATED)
Marcela Derli, E. Novais

We present a novel theoretical approach to incorporate electronic interactions in the study of two-dimensional topological insulators. By exploiting the correspondence between edge state physics and entanglement spectrum in gapped topological systems, we deconstruct the system into one-dimensional channels. This framework enables a simple and elegant inclusion of fermionic interactions into the discussion of topological insulators. We apply this approach to the Kane-Mele model with interactions and magnetic impurities.


Electrostatic shielding effect and Binding energy shift of MoS$_2$, MoSeS$_2$ and MoTeS$_2$ materials. (arXiv:2307.08035v3 [cond-mat.mtrl-sci] UPDATED)
Yaorui Tan, Maolin Bo

In this paper, the electronic structure and bond properties of MoSS$_2$, MoSeS$_2$ and MoTeS$_2$ are studied. Density functional theory (DFT) calculates combined with the binding energy and bond-charge (BBC) model to obtain electronic structure, binding energy shift and bond properties. It is found that electrostatic shielding by electron exchange is the main cause of density fluctuation. A method for calculating the density of Green's function with energy level shift is established. It provides new methods and ideas for the further study of the binding energy, bond states and electronic properties of nanomaterials.


Unconventional optical response in monolayer graphene upon dominant intraband scattering. (arXiv:2307.15945v2 [cond-mat.mes-hall] UPDATED)
Palash Saha, Bala Murali Krishna Mariserla

Scattering dynamics influence the graphenes transport properties and inhibits the charge carrier deterministic behaviour. The intra or inter-band scattering mechanisms are vital for graphenes optical conductivity response under specific considerations of doping. Here, we investigated the influence of scattering systematically on optical conductivity using a semi-classical multiband Boltzmann equation with inclusion of both electron-electron $\&$ electron-phonon collisions. We found unconventional characteristics of linear optical response with a significant deviation from the universal conductivity $\frac{e$^2$}{2$\hbar$}$ in doped monolayer graphene. This is explained through phenomenological relaxation rates under low doping regime with dominant intraband scattering. Such novel optical responses are vanished at high temperatures or overdoping conditions due to strong Drude behaviour. With the aid of approximations around Dirac points we have developed analytical formalism for many body interactions and is in good agreement with the Kubo approaches.


First-principle study of spin transport property in $L1_0$-FePd(001)/graphene heterojunction. (arXiv:2308.02171v3 [cond-mat.mtrl-sci] UPDATED)
Hayato Adachi, Ryuusuke Endo, Hikari Shinya, Hiroshi Naganuma, Mitsuharu Uemoto

In our previous work, we synthesized a metal/2D material heterointerface consisting of $L1_0$-ordered iron-palladium (FePd) and graphene (Gr) called FePd(001)/Gr. This system has been explored by both experimental measurements and theoretical calculations. In this study, we focus on a heterojunction composed of FePd and multilayer graphene referred to as FePd(001)/$m$-Gr/FePd(001), where $m$ represents the number of graphene layers. We perform first-principles calculations to predict their spin-dependent transport properties. The quantitative calculations of spin-resolved conductance and magnetoresistance (MR) ratio (150-200%) suggest that the proposed structure can function as a magnetic tunnel junction in spintronics applications. We also find that an increase in $m$ not only reduces conductance but also changes transport properties from the tunneling behavior to the graphite $\pi$-band-like behavior. Furthermore, we examine the impact of lateral displacements (sliding) at the interface and find that the spin transport properties remain robust despite these changes; this is the advantage of two-dimensional material hetero-interfaces over traditional insulating barrier layers such as MgO.


Disorder-Induced Phase Transitions in Three-Dimensional Chiral Second-Order Topological Insulator. (arXiv:2308.02256v2 [cond-mat.mes-hall] UPDATED)
Yedi Shen, Zeyu Li, Qian Niu, Zhenhua Qiao

Topological insulators have been extended to higher-order versions that possess topological hinge or corner states in lower dimensions. However, their robustness against disorder is still unclear. Here, we theoretically investigate the phase transitions of three-dimensional (3D) chiral second-order topological insulator (SOTI) in the presence of disorders. Our results show that, by increasing disorder strength, the nonzero densities of states of side surface and bulk emerge at critical disorder strengths of $W_{S}$ and $W_{B}$, respectively. The spectral function indicates that the bulk gap is only closed at one of the $R_{4z}\mathcal{T}$-invariant points, i.e., $\Gamma_{3}$. The closing of side surface gap or bulk gap is ascribed to the significant decrease of the elastic mean free time of quasi-particles. Because of the localization of side surface states, we find that the 3D chiral SOTI is robust at an averaged quantized conductance of $2e^{2}/h$ with disorder strength up to $W_{B}$. When the disorder strength is beyond $W_{B}$, the 3D chiral SOTI is then successively driven into two phases, i.e., diffusive metallic phase and Anderson insulating phase. Furthermore, an averaged conductance plateau of $e^{2}/h$ emerges in the diffusive metallic phase.


Isolated Majorana mode in a quantum computer from a duality twist. (arXiv:2308.02387v3 [quant-ph] UPDATED)
Sutapa Samanta, Derek S. Wang, Armin Rahmani, Aditi Mitra

Investigating the interplay of dualities, generalized symmetries, and topological defects beyond theoretical models is an important challenge in condensed matter physics and quantum materials. A simple model exhibiting this physics is the transverse-field Ising model, which can host a noninvertible topological defect that performs the Kramers-Wannier duality transformation. When acting on one point in space, this duality defect imposes the duality twisted boundary condition and binds a single Majorana zero mode. This Majorana zero mode is unusual as it lacks localized partners and has an infinite lifetime, even in finite systems. Using Floquet driving of a closed Ising chain with a duality defect, we generate this Majorana zero mode in a digital quantum computer. We detect the mode by measuring its associated persistent autocorrelation function using an efficient sampling protocol and a compound strategy for error mitigation. We also show that the Majorana zero mode resides at the domain wall between two regions related by a Kramers-Wannier duality. Finally, we highlight the robustness of the isolated Majorana zero mode to integrability and symmetry-breaking perturbations. Our findings offer an approach to investigating exotic topological defects in digitized quantum devices.


Disorder Operator and R\'enyi Entanglement Entropy of Symmetric Mass Generation. (arXiv:2308.07380v2 [cond-mat.str-el] UPDATED)
Zi Hong Liu, Yuan Da Liao, Gaopei Pan, Weilun Jiang, Chao-Ming Jian, Yi-Zhuang You, Fakher F. Assaad, Zi Yang Meng, Cenke Xu

In recent years a consensus has gradually been reached that the previously proposed deconfined quantum critical point (DQCP) for spin-1/2 systems, an archetypal example of quantum phase transition beyond the classic Landau's paradigm, actually does not correspond to a true unitary conformal field theory (CFT). In this work we carefully investigate another type of quantum phase transition supposedly beyond the similar classic paradigm, the so called ``symmetric mass generation" (SMG) transition proposed in recent years. We employ the sharp diagnosis including the scaling of disorder operator and R\'enyi entanglement entropy in large-scale lattice model quantum Monte Carlo simulations. Our results strongly suggest that the SMG transition is indeed an unconventional quantum phase transition and it should correspond to a true $(2+1)d$ unitary CFT.


Non-Hermitian dispersion sign reversal of radiative resonances in two dimensions. (arXiv:2308.09188v2 [cond-mat.mes-hall] UPDATED)
R. Binder, J.S. Schaibley, N.H. Kwong

In a recent publication [Wurdack et al., Nat. Comm. 14:1026 (2023)], it was shown that in microcavities containing atomically thin semiconductors non-Hermitian quantum mechanics can lead to negative exciton polariton masses. We show that mass-sign reversal can occur generally in radiative resonances in two dimensions (without cavity) and derive conditions for it (critical dephasing threshold etc.). In monolayer transition-metal dichalcogenides, this phenomenon is not invalidated by the strong electron-hole exchange interaction, which is known to make the exciton massless.


Excitonic interplay between surface polar III-nitride quantum wells and MoS$_2$ monolayer. (arXiv:2308.10687v3 [cond-mat.mes-hall] UPDATED)
Danxuan Chen, Jin Jiang, Thomas F. K. Weatherley, Jean-François Carlin, Mitali Banerjee, Nicolas Grandjean

III-nitride wide bandgap semiconductors exhibit large exciton binding energies, preserving strong excitonic effects at room temperature. On the other hand, semiconducting two-dimensional (2D) materials, including MoS$_2$, also exhibit strong excitonic effects, attributed to enhanced Coulomb interactions. This study investigates excitonic interactions between surface GaN quantum well (QW) and 2D MoS$_2$ in van der Waals heterostructures by varying the spacing between these two excitonic systems. Optical property investigation first demonstrates the effective passivation of defect states at the GaN surface through MoS$_2$ coating. Furthermore, a strong interplay is observed between MoS$_2$ monolayers and GaN QW excitonic transitions. This highlights the interest of the 2D material/III-nitride QW system to study near-field interactions, such as F\"orster resonance energy transfer, which could open up novel optoelectronic devices based on such hybrid excitonic structures.


Uniqueness of steady states of Gorini-Kossakowski-Sudarshan-Lindblad equations: a simple proof. (arXiv:2309.00335v2 [quant-ph] UPDATED)
Hironobu Yoshida

We present a simple proof of a sufficient condition for the uniqueness of non-equilibrium steady states of Gorini-Kossakowski-Sudarshan-Lindblad equations. We demonstrate the applications of the sufficient condition using examples of the transverse-field Ising model, the XYZ model, and the tight-binding model with dephasing.


Found 18 papers in prb
Date of feed: Wed, 06 Sep 2023 03:17:12 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

${\mathrm{CrTe}}_{2}$ as a two-dimensional material for topological magnetism in complex heterobilayers
Nihad Abuawwad, Manuel dos Santos Dias, Hazem Abusara, and Samir Lounis
Author(s): Nihad Abuawwad, Manuel dos Santos Dias, Hazem Abusara, and Samir Lounis

The discovery of two-dimensional (2D) van der Waals magnetic materials and their heterostructures provided an exciting platform for emerging phenomena with intriguing implications in information technology. Here, based on a multiscale modeling approach that combines first-principles calculations and…


[Phys. Rev. B 108, 094409] Published Tue Sep 05, 2023

Spin squeezing in open Heisenberg spin chains
T. Hernández Yanes, G. Žlabys, M. Płodzień, D. Burba, M. Mackoit Sinkevičienė, E. Witkowska, and G. Juzeliūnas
Author(s): T. Hernández Yanes, G. Žlabys, M. Płodzień, D. Burba, M. Mackoit Sinkevičienė, E. Witkowska, and G. Juzeliūnas

Spin squeezing protocols successfully generate entangled many-body quantum states, the key pillars of the second quantum revolution. In our recent work [Phys. Rev. Lett. 129, 090403 (2022)] we showed that spin squeezing described by the one-axis twisting model can be generated in the Heisenberg spin…


[Phys. Rev. B 108, 104301] Published Tue Sep 05, 2023

Intertwining of lasing and superradiance under spintronic pumping
Oksana Chelpanova, Alessio Lerose, Shu Zhang, Iacopo Carusotto, Yaroslav Tserkovnyak, and Jamir Marino
Author(s): Oksana Chelpanova, Alessio Lerose, Shu Zhang, Iacopo Carusotto, Yaroslav Tserkovnyak, and Jamir Marino

We introduce a quantum optics platform featuring the minimal ingredients for the description of a spintronically pumped magnon condensate, which we use to promote driven-dissipative phase transitions in the context of spintronics. We consider a Dicke model weakly coupled to an out-of-equilibrium bat…


[Phys. Rev. B 108, 104302] Published Tue Sep 05, 2023

Long-range order in arrays of composite and monolithic magnetotoroidal moments
Jannis Lehmann, Naëmi Leo, Laura J. Heyderman, and Manfred Fiebig
Author(s): Jannis Lehmann, Naëmi Leo, Laura J. Heyderman, and Manfred Fiebig

Magnetotoroidal order, also called ferrotoroidicity, is the most recently established type of ferroic state. It is based on a spontaneous and uniform alignment of unit-cell-sized magnetic whirls, called magnetotoroidal moments, associated with a macroscopic toroidization. Because of its intrinsic li…


[Phys. Rev. B 108, 104405] Published Tue Sep 05, 2023

High-precision measurement of the Ferrell-Glover-Tinkham sum rule in a cuprate high-temperature superconductor
R. D. Dawson, X. Shi, K. S. Rabinovich, D. Putzky, Y.-L. Mathis, G. Christiani, G. Logvenov, B. Keimer, and A. V. Boris
Author(s): R. D. Dawson, X. Shi, K. S. Rabinovich, D. Putzky, Y.-L. Mathis, G. Christiani, G. Logvenov, B. Keimer, and A. V. Boris

The authors have combined several complementary spectroscopic methods to achieve high-precision control over the superconductivity-induced spectral weight transfer in a DyBa2Cu3O7 film with a superconducting Tc of 90 K, spanning an energy range over three orders of magnitude from ~1 meV to 1 eV. They find that the Ferrell-Glover-Tinkham sum rule is satisfied within an unprecedented accuracy of 2% by integrating the optical conductivity up to 0.6 eV, consistent with the spectral range of antiferromagnetic spin fluctuations.


[Phys. Rev. B 108, 104501] Published Tue Sep 05, 2023

Massless multifold Hopf semimetals
Ansgar Graf and Frédéric Piéchon
Author(s): Ansgar Graf and Frédéric Piéchon

Three-dimensional massless topological semimetals exhibit linear energy band crossing points that act as monopoles of Berry curvature. Here, an alternative class of massless semimetals is introduced, featuring linear $N$-fold crossing points each of which acts as a source of a Berry dipole. We const…


[Phys. Rev. B 108, 115105] Published Tue Sep 05, 2023

Role of hydrogen bonding in charge-ordered organic conductor $α\text{−}{(\text{BEDT-TTF})}_{2}{\mathrm{I}}_{3}$ probed by $^{127}\mathrm{I}$ nuclear quadrupole resonance
T. Kobayashi, Y. Kato, H. Taniguchi, T. Tsumuraya, K. Hiraki, and S. Fujiyama
Author(s): T. Kobayashi, Y. Kato, H. Taniguchi, T. Tsumuraya, K. Hiraki, and S. Fujiyama

We present $^{127}\mathrm{I}$ nuclear quadrupole resonance spectra and nuclear relaxation of $α\text{−}{(\text{BEDT-TTF})}_{2}{\mathrm{I}}_{3}$ that undergoes a charge-ordering transition. Only one of the two ${\mathrm{I}}_{3}$ anion sites shows a significant differentiation in the electric field gr…


[Phys. Rev. B 108, 115108] Published Tue Sep 05, 2023

Topological junctions in high-Chern-number quantum anomalous Hall systems
Yulei Han, Shiyao Pan, and Zhenhua Qiao
Author(s): Yulei Han, Shiyao Pan, and Zhenhua Qiao

Quantum anomalous Hall effect (QAHE) is the real topological state without magnetic field that is robust against any perturbations, and is related to a bulk topological number $\mathcal{C}$, counting the number of chiral edge modes. Such chiral edge modes also exist at the magnetic domain walls betw…


[Phys. Rev. B 108, 115302] Published Tue Sep 05, 2023

Indication for an anomalous magnetoresistance mechanism in ${(\mathrm{Bi},\mathrm{Sb})}_{2}{(\mathrm{Te},\mathrm{Se})}_{3}$ three-dimensional topological insulator thin films
N. P. Stepina, A. O. Bazhenov, A. V. Shumilin, A. Yu. Kuntsevich, V. V. Kirienko, E. S. Zhdanov, D. V. Ishchenko, and O. E. Tereshchenko
Author(s): N. P. Stepina, A. O. Bazhenov, A. V. Shumilin, A. Yu. Kuntsevich, V. V. Kirienko, E. S. Zhdanov, D. V. Ishchenko, and O. E. Tereshchenko

Electron states with the spin-momentum-locked Dirac dispersion at the surface of a three-dimensional (3D) topological insulator are known to lead to weak antilocalization (WAL), i.e., low temperature and low-magnetic-field quantum interference-induced positive magnetoresistance (MR). In this work, w…


[Phys. Rev. B 108, 115401] Published Tue Sep 05, 2023

Topological ac charge current and continuous invariant in the $α\text{−}{T}_{3}$ lattice under a periodically varying strain
Ruigang Li, Jun-Feng Liu, and Jun Wang
Author(s): Ruigang Li, Jun-Feng Liu, and Jun Wang

Usually, robust invariants in physics take discrete values for the reason of topology, such as integers or fractions in the integer or fractional quantum Hall effect. Here, we show theoretically that the valley Chern number can be responsible for continuous invariants which are insensitive to most p…


[Phys. Rev. B 108, 115403] Published Tue Sep 05, 2023

Corner states of two-dimensional second-order topological insulators with a chiral symmetry and broken time reversal and charge conjugation
Joseph Poata, Fabio Taddei, and Michele Governale
Author(s): Joseph Poata, Fabio Taddei, and Michele Governale

Two-dimensional second-order topological insulators are characterized by the presence of topologically protected zero-energy bound states localized at the corners of a flake. In this paper we theoretically study the occurrence and features of such corner states inside flakes in the shape of a convex…


[Phys. Rev. B 108, 115405] Published Tue Sep 05, 2023

Modeling thermoelectric properties of monolayer and bilayer ${\mathrm{WS}}_{2}$ by including intravalley and intervalley scattering mechanisms
Raveena Gupta and Chandan Bera
Author(s): Raveena Gupta and Chandan Bera

Herein, we investigate the impact of all electron and phonon scattering mechanisms on the electrical and thermal transport properties of the monolayer and bilayer transition-metal dichalcogenide ${\mathrm{WS}}_{2}$. We used the Boltzmann transport equation under the relaxation-time approximation to …


[Phys. Rev. B 108, 115406] Published Tue Sep 05, 2023

Scaling theory of intrinsic Kondo and Hund's rule interactions in magic-angle twisted bilayer graphene
Yang-Zhi Chou and Sankar Das Sarma
Author(s): Yang-Zhi Chou and Sankar Das Sarma

Motivated by the recent studies of intrinsic local moments and Kondo-driven phases in magic-angle twisted bilayer graphene, we investigate the renormalization of Kondo coupling (${J}_{K}$) and the competing Hund's rule interaction ($J$) in the low-energy limit. Specifically, we consider a surrogate …


[Phys. Rev. B 108, 125106] Published Tue Sep 05, 2023

Weiss oscillations in Galilean-invariant Dirac composite fermion theory for even-denominator filling fractions of the lowest Landau level
Yen-Wen Lu, Prashant Kumar, and Michael Mulligan
Author(s): Yen-Wen Lu, Prashant Kumar, and Michael Mulligan

Standard field theoretic formulations of composite fermion theories for the anomalous metals that form at or near even-denominator filling fractions of the lowest Landau level do not possess Galilean invariance. To restore Galilean symmetry, these theories must be supplemented by correction terms. W…


[Phys. Rev. B 108, 125109] Published Tue Sep 05, 2023

Valence transition and termination-dependent surface states in the topological Kondo semimetal YbPtBi
Yuan Fang, Zhongzheng Wu, Guowei Yang, Yuwei Zhang, Weifan Zhu, Yi Wu, Chunyu Guo, Yuke Li, Huiqiu Yuan, Jian-Xin Zhu, Yang Liu, and Chao Cao
Author(s): Yuan Fang, Zhongzheng Wu, Guowei Yang, Yuwei Zhang, Weifan Zhu, Yi Wu, Chunyu Guo, Yuke Li, Huiqiu Yuan, Jian-Xin Zhu, Yang Liu, and Chao Cao

The Yb-terminated and Bi-terminated (111) surface electronic structure of topological Kondo semimetal YbPtBi is investigated using both density-functional-theory (DFT) -based calculations and angle-resolved photoemission spectroscopy (ARPES). The cleavage plane is found to be between Yb-layers and B…


[Phys. Rev. B 108, 125110] Published Tue Sep 05, 2023

Reconstruction, rumpling, and Dirac states at the (001) surface of the topological crystalline insulator ${\text{Pb}}_{1−x}{\text{Sn}}_{x}\text{Se}$
A. Łusakowski, P. Bogusławski, and T. Story
Author(s): A. Łusakowski, P. Bogusławski, and T. Story

The equilibrium atomic configuration and electronic structure of the (001) surface of the IV-VI semiconductors PbTe, PbSe, SnTe, and SnSe are studied using density functional theory methods. At the surfaces of all these compounds, the displacements of ions from their perfect lattice sites reveal two…


[Phys. Rev. B 108, 125201] Published Tue Sep 05, 2023

Topological skin modes and intensity amplification in a nonlinear non-Hermitian lattice
Zhi-Xu Zhang, Ji Cao, Jing-Quan Li, Yu Zhang, Shutian Liu, Shou Zhang, and Hong-Fu Wang
Author(s): Zhi-Xu Zhang, Ji Cao, Jing-Quan Li, Yu Zhang, Shutian Liu, Shou Zhang, and Hong-Fu Wang

Topological lattice systems combined with nonlinearity and non-Hermiticity can give rise to novel solitons, whose exceptional properties are demonstrated in both unique quench dynamics and topological boundary states. Especially, we focus on an Aubry-André-Harper-type lattice with nonlinear hopping …


[Phys. Rev. B 108, 125402] Published Tue Sep 05, 2023

Effects of electric field and interlayer coupling on Schottky barrier of germanene/MoSSe vertical heterojunction
Jun Yuan, Fanfan Wang, Zhufeng Zhang, Baoan Song, Shubin Yan, Ming-Hui Shang, Chaohui Tong, and Jun Zhou
Author(s): Jun Yuan, Fanfan Wang, Zhufeng Zhang, Baoan Song, Shubin Yan, Ming-Hui Shang, Chaohui Tong, and Jun Zhou

Among the many two-dimensional materials, germanene and Janus MoSSe have received considerable attention due to their novel electrical and optical properties. We anticipate that the heterojunction formed by germanene and MoSSe will exhibit exceptional properties and immense potential for application…


[Phys. Rev. B 108, 125404] Published Tue Sep 05, 2023

Found 2 papers in prl
Date of feed: Wed, 06 Sep 2023 03:17:11 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Surprising Charge-Radius Kink in the Sc Isotopes at $N=20$
Kristian König, Stephan Fritzsche, Gaute Hagen, Jason D. Holt, Andrew Klose, Jeremy Lantis, Yuan Liu, Kei Minamisono, Takayuki Miyagi, Witold Nazarewicz, Thomas Papenbrock, Skyy V. Pineda, Robert Powel, and Paul-Gerhard Reinhard
Author(s): Kristian König, Stephan Fritzsche, Gaute Hagen, Jason D. Holt, Andrew Klose, Jeremy Lantis, Yuan Liu, Kei Minamisono, Takayuki Miyagi, Witold Nazarewicz, Thomas Papenbrock, Skyy V. Pineda, Robert Powel, and Paul-Gerhard Reinhard

Charge radii of neutron deficient $^{40}\mathrm{Sc}$ and $^{41}\mathrm{Sc}$ nuclei were determined using collinear laser spectroscopy. With the new data, the chain of Sc charge radii extends below the neutron magic number $N=20$ and shows a pronounced kink, generally taken as a signature of a shell …


[Phys. Rev. Lett. 131, 102501] Published Tue Sep 05, 2023

Imaging-Assisted Single-Photon Doppler-Free Laser Spectroscopy and the Ionization Energy of Metastable Triplet Helium
Gloria Clausen, Simon Scheidegger, Josef A. Agner, Hansjürg Schmutz, and Frédéric Merkt
Author(s): Gloria Clausen, Simon Scheidegger, Josef A. Agner, Hansjürg Schmutz, and Frédéric Merkt

Skimmed supersonic beams provide intense, cold, collision-free samples of atoms and molecules and are one of the most widely used tools in atomic and molecular laser spectroscopy. High-resolution optical spectra are typically recorded in a perpendicular arrangement of laser and supersonic beams to m…


[Phys. Rev. Lett. 131, 103001] Published Tue Sep 05, 2023

Found 1 papers in nano-lett
Date of feed: Tue, 05 Sep 2023 13:08:24 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] Toward High-Peak-to-Valley-Ratio Graphene Resonant Tunneling Diodes
Zihao Zhang, Baoqing Zhang, Yiming Wang, Mingyang Wang, Yifei Zhang, Hu Li, Jiawei Zhang, and Aimin Song

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c02281

Found 1 papers in acs-nano
Date of feed: Tue, 05 Sep 2023 13:04:23 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

[ASAP] On-Surface Synthesis of Graphene Nanoribbons with Atomically Precise Structural Heterogeneities and On-Site Characterizations
Ruoting Yin, Zhengya Wang, Shijing Tan, Chuanxu Ma, and Bing Wang

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c06128

Found 1 papers in nat-comm


Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Topological magneto-optical effect from skyrmion lattice
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