Found 61 papers in cond-mat
Date of feed: Tue, 23 Jan 2024 01:30:00 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)

Topological pumping induced by spatiotemporal modulation of interaction. (arXiv:2401.10906v1 [cond-mat.mes-hall])
Boning Huang, Yongguan Ke, Wenjie Liu, Chaohong Lee

Particle-particle interaction provides a new degree of freedom to induce novel topological phenomena. Here, we propose to use spatiotemporal modulation of interaction to realize topological pumping without single-particle counterpart. Because the modulation breaks time-reversal symmetry, the multiparticle energy bands of bound states have none-zero Chern number, and support topological bound edge states. In a Thouless pump, a bound state that uniformly occupies a topological energy band can be shifted by integer unit cells per cycle, consistent with the corresponding Chern number. We can also realize topological pumping of bound edge state from one end to another. The entanglement entropy between particles rapidly increases at transition points, which is related to the spatial spread of a bounded pair. In addition, we propose to realize hybridized pumping with fractional displacement per cycle by adding an extra tilt potential to separate topological pumping of the bound state and Bloch oscillations of single particle. Our work could trigger further studies of correlated topological phenomena that do not have a single-particle counterpart.

Machine Learning of Knot Topology in Non-Hermitian Band Braids. (arXiv:2401.10908v1 [cond-mat.mes-hall])
Jiangzhi Chen, Zi Wang, Yu-Tao Tan, Ce Wang, Jie Ren

The deep connection among braids, knots and topological physics has provided valuable insights into studying topological states in various physical systems. However, identifying distinct braid groups and knot topology embedded in non-Hermitian systems is challenging and requires significant efforts. Here, we demonstrate that an unsupervised learning with the representation basis of $su(n)$ Lie algebra on $n$-fold extended non-Hermitian bands can fully classify braid group and knot topology therein, without requiring any prior mathematical knowledge or any pre-defined topological invariants. We demonstrate that the approach successfully identifies different topological elements, such as unlink, unknot, Hopf link, Solomon ring, trefoil, and so on, by employing generalized Gell-Mann matrices in non-Hermitian models with $n$=2 and $n$=3 energy bands. Moreover, since eigenstate information of non-Hermitian bands is incorporated in addition to eigenvalues, the approach distinguishes the different parity-time symmetry and breaking phases, recognizes the opposite chirality of braids and knots, and identifies out distinct topological phases that were overlooked before. Our study shows significant potential of machine learning in classification of knots, braid groups, and non-Hermitian topological phases.

Reply to "Comment on `Anomalous Reentrant 5/2 Quantum Hall Phase at Moderate Landau-Level-Mixing Strength' ". (arXiv:2401.10912v1 [cond-mat.mes-hall])
Sudipto Das, Sahana Das, Sudhansu S. Mandal

The proposed $\mathcal{A}$ phase and the corresponding trial wavefunction proposed by Das \emph{et al.} (PRL 131, 056202, 2023) for 5/2 state are argued to describe the fractional quantum Hall liquid state rather than a phase separated or stripe or bubble state.

Symmetry-induced higher-order exceptional points in two dimensions. (arXiv:2401.10913v1 [cond-mat.mes-hall])
Anton Montag, Flore K. Kunst

Exceptional points of order $n$ (EP$n$s) appear in non-Hermitian systems as points where the eigenvalues and eigenvectors coalesce. Whereas EP2s generically appear in two dimensions (2D), higher-order EPs require a higher-dimensional parameter space to emerge. In this work, we provide a complete characterization the appearance of symmetry-induced higher-order EPs in 2D parameter space. We find that besides EP2s only EP3s, EP4s, and EP5s can be stabilized in 2D. Moreover, these higher-order EPs must always appear in pairs with their dispersion determined by the symmetries. Upon studying the complex spectral structure around these EPs, we find that depending on the symmetry, EP3s are accompanied by EP2 arcs, and 2- and 3-level open Fermi structures. Similarly, EP4s and closely related EP5s, which arise due to multiple symmetries, are accompanied by exotic EP arcs and open Fermi structures. For each case, we provide an explicit example. We also comment on the topological charge of these EPs, and discuss similarities and differences between symmetry-protected higher-order EPs and EP2s.

Comment on "Deformations of the spin currents by topological screw dislocation and cosmic dispiration''. (arXiv:2401.10919v1 [cond-mat.mes-hall])
R. R. S. Oliveira

In this comment, we showed that the Dirac equation in the screw dislocation space-time also carries a term that represents the torsion of such topological defect, given by $K_\mu$. Therefore, the Dirac equation worked by Wang et al. is incomplete since such a term was ignored in your equation (what cannot happen). In other words, it is only possible to work with the Dirac equation in the form presented by Wang et al. if the space-time is torsion-free, which is obviously not the case.

A scale-invariant large-area single-mode topological photonic cavity. (arXiv:2401.10928v1 [cond-mat.mes-hall])
Zhongfu Li, Shiqi Li, Bei Yan, Hsun-Chi Chan, Jing Li, Jun Guan, Wengang Bi, Yuanjiang Xiang, Zhen Gao, Shuang Zhang, Peng Zhan, Zhenlin Wang, Biye Xie

Emergent collective modes in lattices give birth to many intriguing physical phenomena in condensed matter physics. Among these collective modes, large-area modes typically feature small level spacings, whilst a single mode tends to be spatially tightly confined. Here, we theoretically propose and experimentally demonstrate a unique scale-invariant, large-area, and single-mode topological cavity mode in a two-dimensional photonic crystal. This mode emerges from the hybridization of the large-area fundamental Dirac mode and in-gap topological corner modes. Remarkably, we find that the scale-invariant, large-area, and single-mode topological cavity mode possesses unique chiralities and with a tunable mode area under the change of the mass term of the inner topological nontrivial lattice. We experimentally observe such topological cavity modes in a 2D photonic system and demonstrate the robustness by introducing disorders in the cavity structure. Our findings have propelled the forefront of higher-order topology research, transitioning it from single-lattice systems to multi-lattice systems and may support promising potential applications, particularly in vertical-cavity surface-emitting lasers.

Mixed state topological order parameters for symmetry protected fermion matter. (arXiv:2401.10993v1 [cond-mat.quant-gas])
Ze-Min Huang, Sebastian Diehl

We construct an observable mixed state topological order parameter for symmetry-protected free fermion matter. It resolves the entire table of topological insulators and superconductors, relying exclusively on the symmetry class, but not on unitary symmetries. It provides a robust, quantized signal not only for pure ground states, but also for mixed states in- or out of thermal equilibrium. Key ingredient is a unitary probe operator, whose phase can be related to spectral asymmetry, in turn revealing the topological properties of the underlying state. This is demonstrated analytically in the continuum limit, and validated numerically on the lattice. The order parameter is experimentally accessible via either interferometry or full counting statistics, for example, in cold atom experiments.

Hybridized magnonic materials for THz frequency applications. (arXiv:2401.11010v1 [cond-mat.mtrl-sci])
D.-Q. To, A. Rai, J. M. O. Zide, S. Law, J. Q. Xiao, M. B. Jungfleisch, M. F. Doty

The capability of magnons to hybridize and strongly couple with diverse excitations offers a promising avenue for realizing and controlling emergent properties that hold significant potential for applications in devices, circuits, and information processing. In this letter, we present recent theoretical and experimental developments in magnon-based hybrid systems, focusing on the combination of magnon excitation in an antiferromagnet with other excitations, namely plasmons in a topological insulator, phonons in a 2D AFM, and photons. The existence of THz frequency magnons, plasmons, and phonons makes magnon-based hybrid systems particularly appealing for high-operating-speed devices. In this context, we explore several directions to advance magnon hybrid systems, including strong coupling between a surface plasmon and magnon polariton in a TI/AFM bilayer, a giant spin Nernst effect induced by magnon phonon coupling in 2D AFMs, and control of magnon-photon coupling using spin torque.

Anti-Jahn-Teller disproportionation and prospects for spin-triplet superconductivity in d-element compounds. (arXiv:2401.11028v1 [cond-mat.supr-con])
A. S. Moskvin, Yu. D. Panov

We argue that the unusual properties of a wide class of materials based on Jahn-Teller 3d and 4d ions with different crystal and electronic structures, from quasi-two-dimensional unconventional superconductors (cuprates, nickelates, ferropnictides/chalcogenides, ruthenate SrRuO4), manganites with local superconductivity to 3D ferrates (CaSr)FeO3, nickelates RNiO3 and silver oxide AgO with unusual charge and magnetic order can be explained within a single scenario. The properties of these materials are related to the instability of their highly symmetric Jahn-Teller "progenitors" with the ground orbital E-state to charge transfer with anti-Jahn-Teller disproportionation and the formation of a system of effective local composite spin-singlet or spin-triplet, electronic or hole bosons moving in a non-magnetic or magnetic lattice. These unusual systems are characterized by an extremely rich variety of phase states from non-magnetic and magnetic insulators to unusual metallic and superconducting states.

Emergent bright excitons with Rashba spin-orbit coupling in atomic monolayers. (arXiv:2401.11079v1 [cond-mat.mes-hall])
Jiayu David Cao, Gaofeng Xu, Benedikt Scharf, Konstantin Denisov, Igor Zutic

Optical properties in van der Waals heterostructures based on monolayer transition-metal dichalcogenides (TMDs), are often dominated by excitonic transitions. While intrinsic spin-orbit coupling (SOC) and an isotropic band structure are typically studied in TMDs, in their heterostructures Rashba SOC and trigonal warping (TW), resulting in bands with threefold anisotropy, are also present. By considering a low-energy effective Hamiltonian and Bethe-Salpeter equation, we study the effect of Rashba SOC and TW on the band structure and absorption spectra. Rashba SOC is predicted to lead to emergent excitons, which are identified as an admixture between 1s and 2p symmetries. In contrast, for experimentally relevant values, TW has only a negligible effect on the absorption spectrum. These findings could guide experimental demonstrations of emergent bright excitons and further studies of the proximity effects in van der Waals heterostructure.

Pressure dependent physical properties of a potential high-TC superconductor ScYH6: insights from first-principles study. (arXiv:2401.11121v1 [cond-mat.mtrl-sci])
Md. Ashraful Alam, F. Parvin, S. H. Naqib

We have investigated the structural, elastic, electronic, thermophysical, superconducting, and optical properties of ScYH6 under uniform hydrostatic pressures up to 25 GPa, using the density functional theory (DFT) formalism. Most of results reported here are novel. The compound ScYH6 has been found to be elastically and thermodynamically stable within the pressure range considered. The compound is brittle; the brittleness decreases with increasing pressure. The elastic anisotropy is low and the machinability index is moderate which increases gradually with rising pressure. The compound is a hard material. The electronic band structure shows weakly metallic character with low density of states at the Fermi level. The Debye temperature of the compound is high and increases with increasing pressure. The Gr\"uneisen parameter of ScYH6 is low and the phonon thermal conductivity is high at room temperature. The compound is a very efficient reflector of infrared radiation. The compound is also an efficient absorber of visible and ultraviolet light. The overall effect of pressure on optical parameters is small. We have also investigated the pressure induced changes in the predicted superconducting state properties by considering the changes in the electronic density of states at the Fermi level, Debye temperature, and the repulsive Coulomb pseudopotential. The superconducting transition temperature is found to increase gradually with increasing pressure.

Valley filtering and valley valves in irradiated pristine graphene. (arXiv:2401.11136v1 [cond-mat.mes-hall])
Rekha Kumari, Gopal Dixit, Arijit Kundu

We theoretically study valley-filtering in pristine graphene irradiated by bicircular counter-rotating laser drive. The dynamical symmetry of the graphene and laser drive disrupts graphene's inversion symmetry, which results distinct quasi-energy states and Floquet band occupations in the two valleys. Controlling the relative phase between the bicircular laser drive ultimately allows to blocks the contribution from one valley while allowing the opposite valley currents in the system. For practical realization of valley-based device, we propose configurational setup for valley filters and valley valve consisting of two graphene nanoribbons irradiated by two bicircular counter-rotating laser drives with a relative phase shift. It is observed that the relative phase between the two bicircular laser drives offer a control knob to generate valley-selective currents and transport responses with very high efficiency by an all-optical way. In addition, our findings about valley filter and valley valve are robust against moderate disorder and modest changes in driving laser parameters. Present work opens an avenue to realise light-based valleytronics devices in reality.

Quasiparticle scattering in three-dimensional topological insulators near the thickness limit. (arXiv:2401.11157v1 [cond-mat.mes-hall])
Haiming Huang, Mu Chen, Dezhi Song, Jun Zhang, Ye-ping Jiang

In the ultra-thin regime, Bi2Te3 films feature two surfaces (with each surface being a two-dimensional Dirac-fermion system) with complicated spin textures and a tunneling term between them. We find in this regime that the quasiparticle scattering is completely different compared with the thick-film case and even behaves differently at each thickness. The thickness-dependent warping effect and tunneling term are found to be the two main factors that govern the scattering behaviors. The inter-band back-scattering that signals the existence of a tunneling term is found to disappear at 4 quintuple layers by the step-edge reflection approach. A four-band model is presented that captures the main features of the thickness-dependent scattering behaviors. Our work clarifies that the prohibition of back-scattering guaranteed by symmetry in topological insulators breaks down in the ultra-thin regime.

Radiation of a short linear antenna above a topologically insulating half-space. (arXiv:2401.11285v1 [cond-mat.mes-hall])
M. Ibarra-Meneses, A. Martín-Ruiz

The topological magnetoelectric effect (TME) is a unique macroscopic manifestation of quantum states of matter possessing topological order and it is described by axion electrodynamics. In three-dimensional topological insulators, for instance, the axion coupling is of the order of the fine structure constant, and hence a perturbative analysis of the field equations is plenty justified. In this paper we use Green's function techniques to obtain time-dependent solutions to the axion field equations in the presence of a planar domain-wall separating two media with different topological order. We apply our results to investigate the radiation of a short linear antenna near the domain-wall.

Optimization of random cost functions and statistical physics. (arXiv:2401.11348v1 [cond-mat.dis-nn])
Andrea Montanari

This is the text of my report presented at the 29th Solvay Conference on Physics on `The Structure and Dynamics of Disordered Systems' held in Bruxelles from October 19 to 21, 2023. I consider the problem of minimizing a random energy function $H(\sigma)$, where $\sigma$ is an $N$-dimensional vector, in the high-dimensional regime $N\gg 1$. Using as a reference point a 1986 paper by Fu and Anderson, I take stock of the progress on this question over the last 40 years. In particular, I focus on the influence and ramifications of ideas originating from statistical physics. My own conclusion is that several of the most fundamental questions in this area (which in 1986 were barely formulated) have now received mathematically rigorous answers, at least in simple -- yet highly nontrivial -- settings. Instrumental to this spectacular progress was the dialogue between different research communities: physics, computer science, mathematics.

Exploring Intrinsic Magnetic Topological Insulators: The Case of EuIn$_2$As$_2$. (arXiv:2401.11386v1 [cond-mat.str-el])
Hao Liu, Qi-Yi Wu, Chen Zhang, Jie Pang, Bo Chen, Jiao-Jiao Song, Yu-Xia Duan, Ya-Hua Yuan, Hai-Yun Liu, Chuan-Cun Shu, Yuan-Feng Xu, You-Guo Shi, Jian-Qiao Meng

In this study, ultrafast optical spectroscopy was employed to elucidate the intricate topological features of EuIn$_2$As$_2$, a promising candidate for a magnetic topological-crystalline axion insulator. Our investigation, focusing on the real-time evolution of topological states, unveiled a narrow surface magnetic gap (2$\Delta_0$ $\simeq$ 8.2 meV)) emerging at the antiferromagnetic transition temperature ($T_N$ $\approx$ 16 K). Below $T_N$, two extremely low-energy collective modes, $\omega_1$ and $\omega_2$, with frequencies of $\sim$9.9 and 21.6 GHz at $T$ = 4 K, respectively, were observed, exhibiting strong temperature dependence. $\omega_1$ correlates with an acoustic phonon, while $\omega_2$ is associated with a magnon. The results suggest that EuIn$_2$As$_2$ has the potential to manifest a magnetic topological-crystalline axion insulator, presenting a small magnetic energy gap on the (001) surface. The findings further our understanding of the interplay between magnetism and topology in this material, showcasing its potential for applications in quantum information processing and spintronics.

Correcting force error-induced underestimation of lattice thermal conductivity in machine learning molecular dynamics. (arXiv:2401.11427v1 [cond-mat.mtrl-sci])
Xiguang Wu, Wenjiang Zhou, Haikuang Dong, Penghua Ying, Yanzhou Wang, Bai Song, Zheyong Fan, Shiyun Xiong

Machine learned potentials (MLPs) have been widely employed in molecular dynamics (MD) simulations to study thermal transport. However, literature results indicate that MLPs generally underestimate the lattice thermal conductivity (LTC) of typical solids. Here, we quantitatively analyze this underestimation in the context of the neuroevolution potential (NEP), which is a representative MLP that balances efficiency and accuracy. Taking crystalline silicon, GaAs, graphene, and PbTe as examples, we reveal that the fitting errors in the machine-learned forces against the reference ones are responsible for the underestimated LTC as they constitute external perturbations to the interatomic forces. Since the force errors of a NEP model and the random forces in the Langevin thermostat both follow a Gaussian distribution, we propose an approach to correcting the LTC by intentionally introducing different levels of force noises via the Langevin thermostat and then extrapolating to the limit of zero force error. Excellent agreement with experiments is obtained by using this correction for all the prototypical materials over a wide range of temperatures. Based on spectral analyses, we find that the LTC underestimation mainly arises from increased phonon scatterings in the low-frequency region caused by the random force errors.

Hydrostatic pressure effect on structural and transport properties of co-existing layered and disordered rock-salt phase of LixCoO2. (arXiv:2401.11446v1 [cond-mat.mtrl-sci])
Thiagarajan Maran (1), A. Jain (2 and 3), Muthukumaran Sundaramoorthy (1 and 5), A. P. Roy (4), Boby Joseph (5), Govindaraj Lingannan (1), Ashwin Mohan (6), D. Bansal (4), S. M. Yusuf (2 and 3), Arumugam Sonachalam (1 and 7). ( (1) Center for High Pressure Research, Bharathidasan University, Tiruchirappalli, India, (2) Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India, (3) Homi Bhabha National Institute, Mumbai, India, (4) Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, India, (5) Elettra - Sincrotrone Trieste, Bosavizza, Italy, (6) Department of Physics, Institute of Chemical Technology, Mumbai, India, (7) Tamil Nadu Open University, Chennai, India. )

It is widely believed that the origin of a significant cause for the voltage and capacity fading observed in lithium (Li)-ion batteries is related to structural modifications occurring in the cathode material during the Li-ion insertion/de-insertion process. The Li-ion insertion/de-insertion mechanism and the resulting structural changes are known to exert a severe strain on the lattice, and consequently leading to performance degradation. Here, with a view to shed more light on the effect of such strain on the structural properties of the cathode material, we have systematically investigated the pressure dependence of structural and transport properties of an LixCoO2 single crystal, grown using 5% excess Li in the precursors. Ambient pressure synchrotron diffraction on these crystals reveals that, the excess Li during the growth, has facilitated the stabilization of a layered rhombohedral phase (space group R3m) as well as a disordered rock-salt phase (space group Fm3m). The volume fraction of the rhombohedral and cubic phase is 60:40, respectively, which remains unchanged up to 10.6 GPa. No structural phase transition has been observed up to 10.6 GPa. An increase in resistance with a decrease in temperature has revealed the semi-metallic nature of the sample. Further, the application of hydrostatic pressure up to 2.8 GPa shows the enhancement of semi-metallic nature. The obtained experimental results can be qualitatively explained via density functional theory (DFT) and thermodynamics modelling. The calculated density of states was reduced, and the activation energy was increased by applied pressure. Our investigations indicate a significant phase stability of the mixed phase crystals under externally applied high pressure and thus suggest the possible use of such mixed phase materials as a cathode in lithium-ion batteries.

Reentrant quantum anomalous Hall effect in molecular beam epitaxy-grown MnBi2Te4 thin films. (arXiv:2401.11450v1 [cond-mat.mes-hall])
Yuanzhao Li, Yunhe Bai, Yang Feng, Jianli Luan, Zongwei Gao, Yang Chen, Yitian Tong, Ruixuan Liu, Su Kong Chong, Kang L. Wang, Xiaodong Zhou, Jian Shen, Jinsong Zhang, Yayu Wang, Chui-Zhen Chen, XinCheng Xie, Xiao Feng, Ke He, Qi-Kun Xue

In this study, we investigate intrinsic magnetic topological insulator MnBi2Te4 thin films grown by molecular beam epitaxy. We observe a reentrant quantum anomalous Hall effect when the Fermi energy enters the valance band and magnetic field equals zero, indicating the emergence of the Chern Anderson insulator state. The discovery opens a new avenue for realizing the QAH effect and underscores the fundamental role of both Berry curvature and Anderson localization.

Fractal Surface States in Three-Dimensional Topological Quasicrystals. (arXiv:2401.11497v1 [cond-mat.mes-hall])
Zhu-Guang Chen, Cunzhong Lou, Kaige Hu, Lih-King Lim

We study topological states of matter in quasicrystals, which do not rely on crystalline orders. In the absence of a bandstructure description and spin-orbit coupling, we show that a three-dimensional quasicrystal can nevertheless form a topological insulator. It relies on a combination of noncrystallographic rotational symmetry of quasicrystals and electronic orbital space symmetry, which is the quasicrystalline counterpart of topological crystalline insulator. The resulting topological state obeys a non-trivial twisted bulk-boundary correspondence and lacks a good metallic surface. The topological surface states, localized on the top and bottom planes respecting the quasicrystalline symmetry, exhibit a new kind of multifractality with probability density concentrates mostly on high symmetry patches. They form a near-degenerate manifold of 'immobile' states whose number scales proportionally with the macroscopic sample size. This can open the door to a novel platform for topological surface physics distinct from the crystalline counterpart.

Topological superconductors in trapped-ion system and their Floquet engineering. (arXiv:2401.11510v1 [quant-ph])
Ming-Jian Gao, Yu-Peng Ma, Jun-Hong An

Obeying non-Abelian statistics, Majorana fermion holds a promise to implement topological quantum computing. It was found that Majorana fermion can be simulated by the zero-energy excitation in a semiconducting nanowire with strong spin-orbit coupling interacting with a $s$-wave superconductor under a magnetic field. We here propose an alternative scheme to simulate the Majorana fermion in a trapped-ion system. Our dimitrized-ion configuration permits us to generate the Majorana modes not only at zero energy but also at the nonzero ones. We also investigate the controllability of the Majorana modes by Floquet engineering. It is found that a widely tunable number of Majorana modes are created on demand by applying a periodic driving on a topologically trivial trapped-ion system. Enriching the platforms for simulating Majorana fermion, our result would open another avenue for realizing topological quantum computing.

Solvable Two-dimensional Dirac Equation with Matrix Potential: Graphene in External Electromagnetic Field. (arXiv:2401.11526v1 [cond-mat.mes-hall])
Mikhail V. Ioffe, David N. Nishnianidze

It is known that the excitations in graphene-like materials in external electromagnetic field are described by solutions of massless two-dimensional Dirac equation which includes both Hermitian off-diagonal matrix and scalar potentials. Up to now, such two-component wave functions were calculated for different forms of external potentials but, as a rule, depending on one spatial variable only. Here, we shall find analytically the solutions for a wide class of combinations of matrix and scalar external potentials which physically correspond to applied mutually orthogonal magnetic and longitudinal electrostatic fields, both depending really on two spatial variables. The main tool for this progress was provided by supersymmetrical (SUSY) intertwining relations, namely, by their most general - asymmetrical - form proposed recently by the authors. Such SUSY-like method is applied in two steps similarly to the second order factorizable (reducible) SUSY transformations in ordinary Quantum Mechanics.

One-dimensional non-Hermitian band structures as Riemann surfaces. (arXiv:2401.11661v1 [math-ph])
Heming Wang, Lingling Fan, Shanhui Fan

We present the viewpoint of treating one-dimensional band structures as Riemann surfaces, linking the unique properties of non-Hermiticity to the geometry and topology of the Riemann surface. Branch cuts and branch points play a significant role when this viewpoint is applied to both the open-boundary spectrum and the braiding structure. An open-boundary spectrum is interpreted as branch cuts connecting certain branch points, and its consistency with the monodromy representation severely limits its possible morphology. A braid word for the Brillouin zone can be read off from its intersections with branch cuts, and its crossing number is given by the winding number of the discriminant. These results open new avenues to generate important insights into the physical behaviors of non-Hermitian systems.

Epitaxial growth and magnetic properties of kagome metal FeSn/elemental ferromagnet heterostructures. (arXiv:2401.11662v1 [cond-mat.mtrl-sci])
Prajwal M. Laxmeesha, Tessa D. Tucker, Rajeev Kumar Rai, Shuchen Li, Myoung-Woo Yoo, Eric A. Stach, Axel Hoffmann, Steven J. May

Binary kagome compounds TmXn (T = Mn, Fe, Co; X = Sn, Ge; m:n = 3:1, 3:2, 1:1) have garnered recent interest owing to the presence of both topological band crossings and flat bands arising from the geometry of the metal-site kagome lattice. To exploit these electronic features for potential applications in spintronics, the growth of high quality heterostructures is required. Here we report the synthesis of Fe/FeSn and Co/FeSn bilayers on Al2O3 substrates using molecular beam epitaxy to realize heterointerfaces between elemental ferromagnetic metals and antiferromagnetic kagome metals. Structural characterization using high-resolution X-ray diffraction, reflection high-energy electron diffraction, and electron microscopy reveals the FeSn films are flat and epitaxial. Rutherford backscattering spectroscopy was used to confirm the stoichiometric window where the FeSn phase is stabilized, while transport and magnetometry measurements were conducted to verify metallicity and magnetic ordering in the films. Exchange bias was observed, confirming the presence of antiferromagnetic order in the FeSn layers, paving the way for future studies of magnetism in kagome heterostructures and potential integration of these materials into devices.

Emergent SU(3) topological system in a trimer SSH model. (arXiv:2401.11695v1 [cond-mat.mes-hall])
Sonu Verma, Tarun Kanti Ghosh

We consider a trimer Su-Schrieffer-Heeger (SSH) tight-binding Hamiltonian keeping up to next-nearest-neighbor (NNN) hopping terms and on-site potential energy. The Bloch Hamiltonian can be expressed in terms of all the eight generators (i.e. Gell-Mann matrices) of the SU(3) group. We provide exact analytical expressions of three dispersive energy bands and the corresponding eigenstates for any choices of the system parameters. The system lacks full chiral symmetry since the energy spectrum is not symmetric around zero, except at isolated Bloch wavevectors. We explore parity, time reversal, and certain special chiral symmetries for various system parameters. We discuss the bulk-boundary correspondence by numerically computing the Zak phase for all the bands and the boundary modes in the open boundary condition. There are three different kinds of topological phase transitions which are classified based on the gap closing points in the Brillouin zone (BZ) while tuning the nearest-neighbor (NN) and NNN hopping terms. We find that quantized changes (in units of $\pi$) in two out of three Zak phases characterize these topological phase transitions. We propose another bulk topological invariant, namely the $\textit{sub-lattice winding number}$, which also characterizes the topological phase transitions changing from $ \nu^{\alpha} = 0 \leftrightarrow 2 $ and $ \nu^{\alpha} = 0 \leftrightarrow 1 \leftrightarrow 2 $ ($\alpha $: sub-lattice index). The sub-lattice winding number provides a relatively simple analytical understanding of topological phases and may help in characterizing topological phases of systems without chiral symmetry.

Gapless symmetry protected topological phases and generalized deconfined critical points from gauging a finite subgroup. (arXiv:2401.11702v1 [cond-mat.str-el])
Lei Su, Meng Zeng

Gauging a finite subgroup of a global symmetry can map conventional phases and phase transitions to unconventional ones. In this work, we study, as a concrete example, an emergent $\mathbb{Z}_2$-gauged system with global symmetry $U(1)$, namely, the $\mathbb{Z}_2$-gauged Bose-Hubbard model both in 1-D and in 2-D. In certain limits, there is an emergent mixed 't Hooft anomaly between the quotient $\tilde{U}(1)$ symmetry and the dual $\hat{\mathbb{Z}}_2$ symmetry. In 1-D, the superfluid phase is mapped to an intrinsically gapless symmetry-protected topological (SPT) phase, as supported by density-matrix renormalization group (DMRG) calculations. In 2-D, the original superfluid-insulator transition becomes a generalized deconfined quantum critical point (DQCP) between a gapless SPT phase, where a SPT order coexists with Goldstone modes, and a $\tilde{U}(1)$-symmetry-enriched topological (SET) phase. We also discuss the stability of these phases and the critical points to small perturbations and their potential experimental realizations. Our work demonstrates that partial gauging is a simple and yet powerful approach in constructing novel phases and quantum criticalities.

Two New Members of the Covalent Organic Frameworks Family: Crystalline 2D-Oxocarbon and 3D-Borocarbon Structures. (arXiv:2401.11843v1 [cond-mat.mtrl-sci])
N. Hassani, A. Movafegh-Ghadirli, Z. Mahdavifar, F. M. Peeters, M. Neek-Amal

While graphene oxide (GO) is representative of a disordered phase of oxocarbons with lackluster electronic properties, the coexistence of ordered, stoichiometric solid-state carbon oxides with graphene brings renewed momentum to the exploration of two-dimensional crystalline oxocarbons. This enduring subject, spanning decades, has recently witnessed significant advancements. In this context, our study delves into a novel material class, COF-66, notable for its meticulously ordered two-dimensional crystalline structure and intrinsic porosity. Employing a global optimization algorithm alongside density-functional calculations, our investigation highlights a standout member within the COF-66 family exceptional quasi-flat oxocarbon (C6O6)exhibiting an unconventional oxygen-decorated pore configuration. This pioneering study introduces C6O6 as an innovative entrant into the crystalline carbon oxide arena, augmenting the established understanding alongside the well-recognized graphene oxide and two graphene monoxide, i.e. {\alpha}-GMO and \b{eta}-GMO. Expanding the exploration, the COF-66 series encompasses 2D-porous carbon nitride (C6N6) and the recently synthesized 2D-porous boroxine (B6O6), adhering to a generalized stoichiometry of X6Y6, where X = B, C, and Y = B, N, O, with X 6= Y. Remarkably, the entire COF-66 ensemble adopts a 2D-crystalline framework, with the exception of C6B6, which assumes a distinct 3D-crystalline arrangement. Employing the PBE (HSE06) level of theory, our electronic structure calculations yield band gap values of 0.01 (0.05) eV, 3.68 (5.29) eV, 0.00 (0.23) eV, and 1.53 (3.09) eV for B6N6, B6O6, C6B6, and C6N6, respectively, reinforcing and aligning with prior investigations.

Quantum Hall criticality in an amorphous Chern insulator. (arXiv:2401.11855v1 [cond-mat.mes-hall])
Soumya Bera, Johannes Dieplinger, Naba P Nayak

We explore the critical properties of a topological transition in a two-dimensional, amorphous lattice with randomly distributed points. The model intrinsically breaks the time-reversal symmetry without an external magnetic field, akin to a Chern insulator. Here, the topological transition is induced by varying the density of lattice points or adjusting the mass parameter. Using the two-terminal conductance and multifractality of the wavefunction, we found that the topological transition belongs to the same universality class as the integer quantum Hall transition. Regardless of the approach to the critical point across the phase boundary, the localization length exponent remains within $\nu \approx 2.55 - 2.61$. The irrelevant scaling exponent for both the observables is $y \approx 0.3(1)$, comparable to the values obtained using transfer matrix analysis in the Chalker-Coddigton network. Additionally, the investigation of the entire distribution function of the inverse participation ratio at the critical point shows possible deviations from the parabolic multifractal spectrum at the anomalous quantum Hall transition.

Coexistence of Topological and Normal Insulating Phases in Electro-Optically Tuned InAs/GaSb Bilayer Quantum Wells. (arXiv:2401.11965v1 [cond-mat.mes-hall])
Manuel Meyer, Tobias Fähndrich, Sebastian Schmid, Adriana Wolf, Sergey Krishtopenko, Benoit Jouault, Gerald Bastard, Frederic Teppe, Fabian Hartmann, Sven Höfling

We report on the coexistence of both normal and topological insulating phases in InAs/GaSb bilayer quantum well induced by the built-in electric field tuned optically and electrically. The emergence of topological and normal insulating phases is assessed based on the evolution of the charge carrier densities, the resistivity dependence of the gap via in-plane magnetic fields and the thermal activation of carriers. For the Hall bar device tuned optically, we observe the fingerprints associated with the presence of only the topological insulating phase. For another Hall bar processed identically but with an additional top gate, the coexistence of normal and topological insulating phases is found by electrical tuning. Our finding paves the way for utilizing a new electro-optical tuning scheme to manipulate InAs/GaSb bilayer quantum wells to obtain trivial-topological insulating interfaces in the bulk rather than at the physical edge of the device.

Nano-optical investigation of grain boundaries, strain and edges in CVD grown MoS$_{2}$ monolayers. (arXiv:2401.11984v1 [cond-mat.mtrl-sci])
Frederico B. Sousa, Rafael Battistella Nadas, Rafael Martins, Ana P. M. Barboza, Jaqueline S. Soares, Bernardo R. A. Neves, Ive Silvestre, Ado Jorio, Leandro M. Malard

The role of defects in two-dimensional semiconductors and how they affect the intrinsic properties of these materials have been a wide researched topic over the past decades. Optical characterization such as photoluminescence and Raman spectroscopies are important tools to probe their physical properties and the impact of defects. However, conventional optical techniques present a spatial resolution limitation lying in a $\mu$m-scale, which can be overcomed by the use of near-field optical measurements. Here, we use tip-enhanced photoluminescence and Raman spectroscopies to unveil nanoscale optical heterogeneities at grain boundaries, local strain fields and edges in grown MoS$_{2}$ monolayers. A noticeable enhancement of the exciton peak intensity corresponding to a trion emission quenching is observed at narrow regions down to 47 nm of width at grain boundaries related to doping effects. Besides, localized strain fields inside the sample lead to non-uniformities in the intensity and energy position of photoluminescence peaks. Finally, distinct samples present different nano-optical responses at their edges due to strain and passivation defects. The passivated defective edges show a photoluminescence intensity enhancement and energy blueshift as well as a frequency blueshift of the 2LA Raman mode. On the other hand, the strained edges display a photoluminescence energy redshift and frequency redshifts for E$_{2g}$ and 2LA Raman modes. Our work shows that different defect features can be only probed by using optical spectroscopies with a nanometric resolution, thus revealing hindered local impact of different nanoscale defects in two-dimensional materials.

Interplay of Landau quantization and interminivalley scatterings in a weakly coupled moir\'e superlattice. (arXiv:2401.12003v1 [cond-mat.mes-hall])
Yalong Yuan, Le Liu, Jundong Zhu, Jingwei Dong, Yanbang Chu, Fanfan Wu, Luojun Du, Kenji Watanabe, Takashi Taniguchi, Dongxia Shi, Guangyu Zhang, Wei Yang

Double layer quantum systems are promising platforms for realizing novel quantum phases. Here, we report a study of quantum oscillations (QOs) in a weakly coupled double layer system, composed of a large angle twisted double bilayer graphene (TDBG). We observe two different QOs at low temperature, one with a periodicity in carrier density (n), i.e. Shubnikov de Haas oscillation (SdHO) due to Landau quantization, and the other one in displacement field (D), resulting a grid pattern. We quantify the interlayer coupling strength by measuring the interlayer capacitance from the grid pattern with a capacitance model, revealing an electron hole asymmetry. At high temperature when SdHO are thermal smeared, we observe resistance peaks when LLs from two minivalleys in the moir\'e Brillion zone are aligned, regardless of carrier density; eventually, it results in a two fold increase of oscillating frequency in D, serving as a smoking gun evidence of the magneto intersubband oscillations (MISO) in a double layer system. The temperature dependence of MISO suggests electron-electron interaction between two minivalleys play a crucial rule in the scattering, and the scattering times obtained from MISO thermal damping are found to be correlated with the interlayer coupling strength. Our study reveals an intriguing interplay among Landau quantization, moir\'e band structure, and scatterings.

Machine Learning Based Prediction of Polaron-Vacancy Patterns on the TiO$_2$(110) Surface. (arXiv:2401.12042v1 [cond-mat.mtrl-sci])
Viktor C. Birschitzky, Igor Sokolovic, Michael Prezzi, Krisztian Palotas, Martin Setvin, Ulrike Diebold, Michele Reticcioli, Cesare Franchini

The multifaceted physics of oxides is shaped by their composition and the presence of defects, which are often accompanied by the formation of polarons. The simultaneous presence of polarons and defects, and their complex interactions, pose challenges for first-principles simulations and experimental techniques. In this study, we leverage machine learning and a first-principles database to analyze the distribution of surface oxygen vacancies (V$_{\rm O}$) and induced small polarons on rutile TiO$_2$(110), effectively disentangling the interactions between polarons and defects. By combining neural-network supervised learning and simulated annealing, we elucidate the inhomogeneous V$_{\rm O}$ distribution observed in scanning probe microscopy (SPM). Our innovative approach allows us to understand and predict defective surface patterns at previously inaccessible length scales, identifying the specific role of individual types of defects. Specifically, surface-polaron-stabilizing V$_{\rm O}$-configurations are identified, which could have consequences for surface reactivity.

Temperature as Joules per Bit. (arXiv:2401.12119v1 [quant-ph])
Charles Alexandre Bédard, Sophie Berthelette, Xavier Coiteux-Roy, Stefan Wolf

Boltzmann's constant reflects a historical misunderstanding of the concept of entropy, whose informational nature is obfuscated when expressed in J/K. We suggest that the development of temperature and energy, historically prior to that of entropy, does not amount to their logical priority: Temperature should be defined in terms of entropy, not vice versa. Following the precepts of information theory, entropy is measured in bits, and coincides with information capacity at thermodynamic equilibrium. Consequently, not only is the temperature of an equilibrated system expressed in J/bit, but it acquires an operational meaning: It is the cost in energy to increase its information capacity by 1 bit. Our proposal also supports the notion of available capacity, analogous to free energy. Finally, it simplifies Landauer's cost and clarifies that it is a cost of displacement, not of erasure.

Machine-learning structural reconstructions for accelerated point defect calculations. (arXiv:2401.12127v1 [cond-mat.mtrl-sci])
Irea Mosquera-Lois, Seán R. Kavanagh, Alex M. Ganose, Aron Walsh

Defects dictate the properties of many functional materials. To understand the behaviour of defects and their impact on physical properties, it is necessary to identify the most stable defect geometries. However, global structure searching is computationally challenging for high-throughput defect studies or materials with complex defect landscapes, like alloys or disordered solids. Here, we tackle this limitation by harnessing a machine-learning surrogate model to qualitatively explore the defect structural landscape. By learning defect motifs in a family of related metal chalcogenide and mixed anion crystals, the model successfully predicts favourable reconstructions for unseen defects in unseen compositions for 90% of cases, thereby reducing the number of first-principles calculations by 73%. Using CdSe$_x$Te$_{1-x}$ alloys as an exemplar, we train a model on the end member compositions and apply it to find the stable geometries of all inequivalent vacancies for a range of mixing concentrations, thus enabling more accurate and faster defect studies for configurational complex systems.

Time-Resolved Imaging Reveals Transiently Chaotic Spin-Orbit-Torque-Driven Dynamics Under Controlled Conditions. (arXiv:2401.12130v1 [cond-mat.mes-hall])
Lisa-Marie Kern, Kai Litzius, Victor Deinhart, Michael Schneider, Christopher Klose, Kathinka Gerlinger, Riccardo Battistelli, Dieter Engel, Christian M. Günther, Meng-Jie Huang, Katja Höflich, Felix Büttner, Stefan Eisebitt, Bastian Pfau

Spin-orbit torques (SOTs) act as efficient drivers for nanoscale magnetic systems, such as in magnetic tunnel junctions, nano-oscillators and racetrack geometries. In particular, in combination with materials exhibiting high Dzyaloshinskii--Moriya interaction, SOTs are considered to result in well-controlled deterministic magnetisation dynamics and are, therefore, used as robust drives to move and create magnetic skyrmions. In contrast to these expectations, we here find unpredictable, transiently chaotic dynamics induced by SOT at an artificial anisotropy-engineered defect in a magnetic racetrack. Based on these controlled conditions, we directly observe the nanoscale dynamics with holography-based, time-resolved x-ray imaging. In concert with micromagnetic simulations, we disclose a regime of violent picosecond fluctuations, including topological instabilities that, remarkably, result in deterministic final configurations. In addition, our images expose previously unseen skyrmion shedding and highlight the potential of transiently chaotic pathways for topological switching. Our approach offers new perspectives for the investigation and application of highly non-linear SOT dynamics in spintronics materials.

Laser cooling of a fermionic molecule. (arXiv:2401.12145v1 [physics.atom-ph])
Jinyu Dai, Qi Sun, Benjamin C. Riley, Debayan Mitra, Tanya Zelevinsky

Only bosonic molecular species have been directly laser cooled to date, primarily due to an abundance of bosonic isotopes in nature and to their simpler hyperfine structure. Fermionic molecules provide new opportunities for ultracold chemistry, quantum simulation, and precision measurements. Here we report direct laser cooling of a fermionic molecular isotopologue, calcium monodeuteride (CaD). With a nuclear spin I = 1, only 5 hyperfine states need to be addressed for rotational closure in optical cycling. These hyperfine states are unresolved for typical experimental linewidths. We present a method for efficiently producing alkaline-earth metal hydrides and deuterides. We demonstrate rotational closure and show magnetically assisted Sisyphus cooling in one dimension for a beam of CaD molecules. Our results indicate that the experimental complexity for laser cooling CaD is similar to that of calcium monohydride (CaH). Laser cooling of CaD is a promising first step for production of ultracold and trapped atomic deuterium.

Superfluidity of indirect momentum space dark dipolar excitons in a double layer with massive anisotropic tilted semi-Dirac bands. (arXiv:2401.12154v1 [cond-mat.mes-hall])
A. Nafis Arafat, Oleg L. Berman, Godfrey Gumbs

We have theoretically investigated the spin- and valley-dependent superfluidity properties of indirect momentum space dark dipolar excitons in double layers with massive anisotropic tilted semi-Dirac bands in the presence of circularly polarized irradiation. An external vertical electric field is also applied to the structure and is responsible for tilting and gap opening for the band structure. For our calculations we used the parameters of a double layer of 1T$^\prime$-MoS$_2$. Closed form analytical expressions are presented for the energy spectrum for excitons, their associated wave functions and binding energies. Additionally, we examine the effects which the intensity and frequency of circularly polarized irradiation has for 1T$^\prime$-MoS$_2$ on the effective mass of the excitons since it has been demonstrated that the application of an external high-frequency dressing field tailors the crucial electronic including the exciton binding energy, as well as the critical temperature for superfluidity. We also calculate the sound velocity in the anisotropic weakly-interacting Bose gas of two-component indirect momentum space dark excitons for a double layer of 1T$^\prime$-MoS$_2$. We show that the critical velocity of superfluidity, the spectrum of collective excitations, concentrations of the superfluid and normal component, and mean field critical temperature for superfluidity are anisotropic and formed by a two-component system. The critical temperature for superfluidity is increased when the exciton concentration and interlayer separation are increased. We propose the use of phonon-assisted photoluminescence to experimentally confirm directional superfluidity of indirect momentum space dark excitons in a double layer with massive anisotropic tilted semi-Dirac bands.

Dirac zeros in an orbital selective Mott phase: Green's function Berry curvature and flux quantization. (arXiv:2401.12156v1 [cond-mat.str-el])
Lei Chen, Haoyu Hu, Maia G. Vergniory, Jennifer Cano, Qimiao Si

How electronic topology develops in strongly correlated systems represents a fundamental challenge in the field of quantum materials. Recent studies have advanced the characterization and diagnosis of topology in Mott insulators whose underlying electronic structure is topologically nontrivial, through ``Green's function zeros". However, their counterparts in metallic systems have yet to be explored. Here, we address this problem in an orbital-selective Mott phase (OSMP), which is of extensive interest to a variety of strongly correlated systems with a short-range Coulomb repulsion. We demonstrate symmetry protected crossing of the zeros in an OSMP. Utilizing the concept of Green's function Berry curvature, we show that the zero crossing has a quantized Berry flux. The resulting notion of Dirac zeros provides a window into the largely hidden landscape of topological zeros in strongly correlated metallic systems and, moreover, opens up a means to diagnose strongly correlated topology in new materials classes.

Toward new scaling laws for wrinkling in biologically relevant fiber-reinforced bilayers. (arXiv:2401.12157v1 [cond-mat.soft])
A. Mirandola, A. Cutolo, A. R. Carotenuto, N. Nguyen, L. Pocivavsek, M. Fraldi, L. Deseri

Wrinkling, creasing and folding are frequent phenomena encountered in biological and man-made bilayers made by thin films bonded to thicker and softer substrates often containing fibers. Paradigmatic examples of the latter are the skin, the brain, and arterial walls, for which wiggly cross-sections are detected. Although experimental investigations on corrugation of these and analog bilayers would greatly benefit from scaling laws for prompt comparison of the wrinkling features, neither are they available nor have systematic approaches yielding to such laws ever been provided before. This gap is filled in this paper, where a uniaxially compressed bilayer formed by a thin elastic film bonded on a hyperelastic fiber-reinforced substrate is considered. The force balance at the film-substrate interface is here analytically and numerically investigated for highly mismatched film-substrates. The onset of wrinkling is then characterized in terms of both the critical strain and its corresponding wavenumber. Inspired by the asymptotic laws available for neo-Hookean bilayers, the paper then provides a systematic way to achieve novel scaling laws for the wrinkling features for fiber-reinforced highly mismatched hyperelastic bilayers. Such novel scaling laws shed light on the key contributions defining the response of the bilayer, as it is characterized by a fiber-induced complex anisotropy. Results are compared with Finite Element Analyses and also with outcomes of both existing linear models and available adhoc scalings. Furthermore, the amplitude, the global maximum and minimum of ruga occurring under increasing compression spanning the wrinkling, period doubling and folding regimes are also obtained.

Identifying gap-closings in open non-Hermitian systems by Biorthogonal Polarization. (arXiv:2401.12213v1 [quant-ph])
Ipsita Mandal

We investigate gap-closings in one- and two-dimensional tight-binding models with two bands, containing non-Hermitian hopping terms, and open boundary conditions (OBCs) imposed along one direction. We compare the bulk OBC spectra with the periodic boundary condition (PBC) spectra, pointing out that they do not coincide, which is an intrinsic characteristic of non-Hermitian systems. The non-Hermiticity thus results in the failure of the familiar notions of bulk-boundary correspondence found for Hermitian systems. This necessitates the search for topological invariants which can characterize gap-closings in open non-Hermitian systems correctly and unambiguously. We elucidate the behaviour of two possible candidates applicable for one-dimensional slices -- (1) the sum of winding numbers for the two bands defined on a generalized Brillouin zone and (2) the biorthogonal polarization (BP). While the former shows jumps/discontinuities for some of the non-Hermitian systems studied here, at points when an edge mode enters the bulk states and becomes delocalized, it does not maintain quantized values in a given topological phase. On the contrary, BP shows jumps and at phase transitions takes the quantized value of one or zero, which corresponds to whether an actual edge mode exists or whether that mode is delocalized and absorbed within the bulk (not being an edge mode anymore).

Fast barrier-free switching in synthetic antiferromagnets. (arXiv:2110.02138v3 [cond-mat.mes-hall] UPDATED)
Yu. Dzhezherya, V. Kalita, P. Polynchuk, A. Kravets, V. Korenivski, S. Kruchinin, S. Bellucci

We analytically solve the Landau-Lifshitz equations for the collective magnetization dynamics in a synthetic antiferromagnet (SAF) nanoparticle and uncover a regime of barrier-free switching under a short small-amplitude magnetic field pulse applied perpendicular to the SAF plane. We give examples of specific implementations for forming such low-power and ultra-fast switching pulses. For fully optical, resonant, barrier-free SAF switching we estimate the power per write operation to be $ \sim 100 $ pJ, 10-100 times smaller than for conventional quasi-static rotation, which should be attractive for memory applications.

Transcription-induced active forces suppress chromatin motion. (arXiv:2205.00353v4 [] UPDATED)
Sucheol Shin, Guang Shi, Hyun Woo Cho, D. Thirumalai

The organization of interphase chromosomes in a number of species is starting to emerge thanks to advances in a variety of experimental techniques. However, much less is known about the dynamics, especially in the functional states of chromatin. Some experiments have shown that the motility of individual loci in human interphase chromosome decreases during transcription, and increases upon inhibiting transcription. This is a counter-intuitive finding because it is thought that the active mechanical force ($F$) on the order of ten pico-newtons, generated by RNA polymerase II (RNAPII) that is presumably transmitted to the gene-rich region of the chromatin, would render it more open, thus enhancing the mobility. We developed a minimal active copolymer model for interphase chromosomes to investigate how $F$ affects the dynamical properties of chromatin. The movements of the loci in the gene-rich region are suppressed in an intermediate range of $F$, and are enhanced at small $F$ values, which has also been observed in experiments. In the intermediate $F$, the bond length between consecutive loci increases, becoming commensurate with the distance at the minimum of the attractive interaction between non-bonded loci. This results in a transient disorder-to-order transition, leading to a decreased mobility during transcription. Strikingly, the $F$-dependent change in the locus dynamics preserves the organization of the chromosome at $F=0$. Transient ordering of the loci, which is not found in the polymers with random epigenetic profiles, in the gene-rich region might be a plausible mechanism for nucleating a dynamic network involving transcription factors, RNAPII, and chromatin.

Liouville conformal blocks and Stokes phenomena. (arXiv:2301.07957v2 [hep-th] UPDATED)
Xia Gu, Babak Haghighat

In this work we derive braid group representations and Stokes matrices for Liouville conformal blocks with one irregular operator. By employing the Coulomb gas formalism, the corresponding conformal blocks can be interpreted as wavefunctions of a Landau-Ginzburg model specified by a superpotential $\mathcal{W}$. Alternatively, these can also be viewed as wavefunctions of a 3d TQFT on a 3-ball with boundary a 2-sphere on which the operator insertions represent Anyons whose fusion rules describe novel topological phases of matter.

Twisted curve geometry underlying topological invariants. (arXiv:2304.06240v3 [nlin.PS] UPDATED)
Radha Balakrishnan, Rossen Dandoloff, Avadh Saxena

Topological invariants such as winding numbers and linking numbers appear as charges of topological solitons in diverse nonlinear physical systems described by a unit vector field defined on two and three dimensional manifolds. While the Gauss-Bonnet theorem shows that the Euler characteristic (a topological invariant) can be written as the integral of the Gaussian curvature (an intrinsic geometric quantity), the intriguing question of whether winding and linking numbers can also be expressed similarly as integrals of some intrinsic geometric quantities has not been addressed in the literature. In this paper we provide the answer by showing that for the winding number in two dimensions, these quantities are torsions of the two evolving space curves describing the manifold. On the other hand, in three dimensions we find that in addition to torsions, intrinsic twists of the space curves are necessary to obtain a nontrivial winding number and linking number. These new results arise from the hitherto unknown connections that we establish between these topological invariants and the corresponding appropriately normalized global anholonomies (i.e., geometric phases) associated with the unit vector fields on the respective manifolds. An application of our results to a 3D Heisenberg ferromagnetic model supporting a topological soliton is also presented.

Quantum oscillations revealing topological band in kagome metal ScV6Sn6. (arXiv:2305.04683v2 [cond-mat.mtrl-sci] UPDATED)
Changjiang Yi, Xiaolong Feng, Ning Mao, Premakumar Yanda, Subhajit Roychowdhury, Yang Zhang, Claudia Felser, Chandra Shekhar

Compounds with kagome lattice structure are known to exhibit Dirac cones, flat bands, and van Hove singularities, which host numerous versatile quantum phenomena. Inspired by these intriguing properties, we investigate the temperature and magnetic field dependent electrical transports along with the theoretical calculations of ScV6Sn6, a nonmagnetic charge density wave (CDW) compound. At low temperatures, the compound exhibits Shubnikov-de Haas quantum oscillations, which help to design the Fermi surface (FS) topology. This analysis reveals the existence of several small FSs in the Brillouin zone, combined with a large FS. Among them, the FS possessing Dirac band is a non-trivial and generates a non-zero Berry phase. In addition, the compound also shows the anomalous Hall-like behaviour up to the CDW with the CDW phase, ScV6Sn6 presents a unique material example of the versatile HfFe6Ge6 family and provides various promising opportunities to explore the series further.

Weakened Topological Protection of the Quantum Hall Effect in a Cavity. (arXiv:2305.10558v3 [cond-mat.mes-hall] UPDATED)
Vasil Rokaj, Jie Wang, John Sous, Markus Penz, Michael Ruggenthaler, Angel Rubio

We study the quantum Hall effect in a two-dimensional homogeneous electron gas coupled to a quantum cavity field. As initially pointed out by Kohn, Galilean invariance for a homogeneous quantum Hall system implies that the electronic center of mass (CM) decouples from the electron-electron interaction, and the energy of the CM mode, also known as Kohn mode, is equal to the single particle cyclotron transition. In this work, we point out that strong light-matter hybridization between the Kohn mode and the cavity photons gives rise to collective hybrid modes between the Landau levels and the photons. We provide the exact solution for the collective Landau polaritons and we demonstrate the weakening of topological protection at zero temperature due to the existence of the lower polariton mode which is softer than the Kohn mode. This provides an intrinsic mechanism for the recently observed topological breakdown of the quantum Hall effect in a cavity [Appugliese et al., Science 375, 1030-1034 (2022)]. Importantly, our theory predicts the cavity suppression of the thermal activation gap in the quantum Hall transport. Our work paves the way for future developments in the cavity control of quantum materials.

Interaction-induced Liouvillian skin effect in a fermionic chain with a two-body loss. (arXiv:2305.19697v2 [cond-mat.str-el] UPDATED)
Shu Hamanaka, Kazuki Yamamoto, Tsuneya Yoshida

Despite recent intensive research on topological aspects of open quantum systems, effects of strong interactions have not been sufficiently explored. In this paper, we demonstrate that complex-valued interactions induce the Liouvillian skin effect by analyzing a one-dimensional correlated model with two-body loss. We show that, in the presence of complex-valued interactions, eigenmodes and eigenvalues of the Liouvillian strongly depend on boundary conditions. Specifically, we find that complex-valued interactions induce localization of eigenmodes of the Liouvillian around the right edge under open boundary conditions. To characterize the Liouvllian skin effect, we define the topological invariant by using the Liouvillian superoperator. Then, we numerically confirm that the topological invariant captures the Liouvillian skin effect. Furthermore, the presence of the localization of eigenmodes results in the unique dynamics observed only under open boundary conditions: particle accumulation at the right edge in transient dynamics. Our result paves the way to realize topological phenomena in open quantum systems induced by strong interactions.

Temperature Dependent Failure of Atomically Thin MoTe2. (arXiv:2306.14733v3 [cond-mat.mtrl-sci] UPDATED)
A S M Redwan Haider, Ahmad Fatehi Ali Mohammed Hezam, Md Akibul Islam, Yeasir Arafat, Mohammad Tanvirul Ferdaous, Sayedus Salehin, Md.Rezwanul Karim

In this study, we systematically investigated the mechanical responses of monolayer molybdenum ditelluride (MoTe2) using molecular dynamics (MD) simulations. The tensile behavior of trigonal prismatic phase (2H phase) MoTe2 under uniaxial strain was simulated in the armchair and zigzag directions. We also investigated the crack formation and propagation in both armchair and zigzag directions at 10K and 300K to understand the fracture behavior of monolayer MoTe2 at different temperatures. The MD simulations show clean cleavage for the armchair direction, and the cracks were numerous and scattered in the case of the zigzag direction. Finally, we investigated the effect of temperature on Young's modulus and fracture stress of monolayer MoTe2. The results show that at a strain rate of 10^-4 ps^-1, the fracture strength of monolayer MoTe2 in the armchair and zigzag directions at 10K is 16.33 GPa (11.43 N/m) and 13.71 GPa (9.46 N/m) under a 24% and 18% fracture strain, respectively. The fracture strength of monolayer MoTe2 in the armchair and zigzag direction at 600K is 10.81 GPa (7.56 N/m) and 10.13 GPa (7.09 N/m) under a 12.5% and 12.47% fracture strain, respectively.

Nonlinear Valley Hall Effect. (arXiv:2307.12088v2 [cond-mat.mes-hall] UPDATED)
Kamal Das, Koushik Ghorai, Dimitrie Culcer, Amit Agarwal

The valley Hall effect arises from valley contrasting Berry curvature and requires inversion symmetry breaking. Here, we propose a nonlinear mechanism to generate a valley Hall current in systems with both inversion and time-reversal symmetry, where the linear and second-order charge Hall currents vanish along with the linear valley Hall current. We show that a second-order valley Hall signal emerges from the electric field correction to the Berry curvature, provided a valley-contrasting anisotropic dispersion is engineered. We demonstrate the nonlinear valley Hall effect in tilted massless Dirac fermions in strained graphene and organic semiconductors. Our work opens up the possibility of controlling the valley degree of freedom in inversion symmetric systems via nonlinear valleytronics.

High-Order Topological Phase Diagram Revealed by Anomalous Nernst Effect in Janus ScClI Monolayer. (arXiv:2308.07550v2 [cond-mat.mes-hall] UPDATED)
Ning-Jing Yang, Jian-Min Zhang

Higher-order topological properties of two-dimensional(2D) magnetic materials have recently been proposed. In 2D ferromagnetic Janus materials, we find that ScClI is a second-order topological insulator (SOTI). By means of a multi-orbital tight-binding model, we analyze the orbital contributions of higher-order topologies. Further, we give the complete high-order topological phase diagram of ScClI, based on the external field modulation of the magneto-valley coupling and energy levels. 2D ScClI has a pronounced valley polarization, which causes different insulating phases to exhibit completely different anomalous Nernst conductance. As a result, we use the matched anomalous Nernst effect to reveal the topological phase transition process of ScClI. We utilize the characteristics of valley electronics to link higher-order topological materials with the anomalous Nernst effect, which has potential implications for high-order topological insulators and valley electronics.

Dissipation driven dynamical topological phase transitions in two-dimensional superconductors. (arXiv:2308.08265v2 [cond-mat.str-el] UPDATED)
Andrea Nava, Carmine Antonio Perroni, Reinhold Egger, Luca Lepori, Domenico Giuliano

We induce and study a topological dynamical phase transition between two planar superconducting phases. Using the

Lindblad equation to account for the interactions of Bogoliubov quasiparticles among themselves

and with the fluctuations of the superconducting order parameter, we derive the relaxation dynamics

of the order parameter. To characterize the phase transition, we compute the fidelity and the

spin-Hall conductance of the open system.

Our approach provides crucial informations for experimental implementations, such as

the dependence of the critical time on the system-bath coupling.

Hamiltonian learning with real-space impurity tomography in topological moire superconductors. (arXiv:2308.11400v2 [cond-mat.mes-hall] UPDATED)
Maryam Khosravian, Rouven Koch, Jose L. Lado

Extracting Hamiltonian parameters from available experimental data is a challenge in quantum materials. In particular, real-space spectroscopy methods such as scanning tunneling spectroscopy allow probing electronic states with atomic resolution, yet even in those instances extracting effective Hamiltonian is an open challenge. Here we show that impurity states in modulated systems provide a promising approach to extracting non-trivial Hamiltonian parameters of a quantum material. We show that by combining the real-space spectroscopy of different impurity locations in a moire topological superconductor, modulations of exchange and superconducting parameters can be inferred via machine learning. We demonstrate our strategy with a physically-inspired harmonic expansion combined with a fully-connected neural network that we benchmark against a conventional convolutional architecture. We show that while both approaches allow extracting exchange modulations, only the former approach allows inferring the features of the superconducting order. Our results demonstrate the potential of machine learning methods to extract Hamiltonian parameters by real-space impurity spectroscopy as local probes of a topological state.

Probing quantum spin liquids with a quantum twisting microscope. (arXiv:2308.15533v2 [cond-mat.str-el] UPDATED)
Valerio Peri, Shahal Ilani, Patrick A. Lee, Gil Refael

The experimental characterization of quantum spin liquids poses significant challenges due to the absence of long-range magnetic order, even at absolute zero temperature. The identification of these states of matter often relies on the analysis of their excitations. In this paper, we propose a method for detecting the signatures of the fractionalized excitations in quantum spin liquids using a tunneling spectroscopy setup. Inspired by the recent development of the quantum twisting microscope, we consider a planar tunneling junction, in which a candidate quantum spin liquid material is placed between two graphene layers. By tuning the relative twist angle and voltage bias between the leads, we can extract the dynamical spin structure factor of the tunneling barrier with momentum and energy resolution. Our proposal presents a promising tool for experimentally characterizing quantum spin liquids in two-dimensional materials.

On the dynamical stability of copper-doped lead apatite. (arXiv:2309.11541v3 [cond-mat.supr-con] UPDATED)
Sun-Woo Kim, Kang Wang, Siyu Chen, Lewis J. Conway, G. Lucian Pascut, Ion Errea, Chris J. Pickard, Bartomeu Monserrat

The recent claim of room temperature superconductivity in a copper-doped lead apatite compound, called LK-99, has sparked remarkable interest and controversy. Subsequent experiments have largely failed to reproduce the claimed superconductivity, while theoretical works have identified multiple key features including strong electronic correlation, structural instabilities, and dopability constraints. A puzzling claim of several recent theoretical studies is that both parent and copper-doped lead apatite structures are dynamically unstable at the harmonic level, questioning decades of experimental reports of the parent compound structures and the recently proposed copper-doped structures. In this work, we demonstrate that both parent and copper-doped lead apatite structures are dynamically stable at room temperature. Anharmonic phonon-phonon interactions play a key role in stabilizing some copper-doped phases, while most phases are largely stable even at the harmonic level. We also show that dynamical stability depends on both volume and correlation strength, suggesting controllable ways of exploring the copper-doped lead apatite structural phase diagram. Our results fully reconcile the theoretical description of the structures of both parent and copper-doped lead apatite with experiment.

Localization transition in non-Hermitian systems depending on reciprocity and hopping asymmetry. (arXiv:2310.03412v2 [cond-mat.dis-nn] UPDATED)
Daniil Kochergin, Vasilii Tiselko, Arsenii Onuchin

We studied the single-particle Anderson localization problem for non-Hermitian systems on directed graphs. Random regular graph and various undirected standard random graph models were modified by controlling reciprocity and hopping asymmetry parameters. We found the emergence of left, biorthogonal and right localized states depending on both parameters and graph structure properties such as node degree $d$. For directed random graphs, the occurrence of biorthogonal localization near exceptional points is described analytically and numerically. The clustering of localized states near the center of the spectrum and the corresponding mobility edge for left and right states are shown numerically. Structural features responsible for localization, such as topologically invariant nodes or drains and sources, were also described. Considering the diagonal disorder, we observed the disappearance of localization dependence on reciprocity around $W \sim 20$ for a random regular graph $d=4$. With a small diagonal disorder, the average biorthogonal fractal dimension drastically reduces. Around $W \sim 5$ localization scars occur within the spectrum, alternating as vertical bands of clustering of left and right localized states.

Einstein-de Haas torque as a discrete spectroscopic probe allows nanomechanical measurement of a magnetic resonance. (arXiv:2310.18546v2 [cond-mat.mes-hall] UPDATED)
K.R. Fast, J.E. Losby, G. Hajisalem, P.E. Barclay, M.R. Freeman

The Einstein-de Haas (EdH) effect is a fundamental, mechanical consequence of any temporal change of magnetism in an object. EdH torque results from conserving the object's total angular momentum: the angular momenta of all the specimen's magnetic moments, together with its mechanical angular momentum. Although the EdH effect is usually small and difficult to observe, it increases in magnitude with detection frequency. We explore the frequency-dependence of EdH torque for a thin film permalloy microstructure by employing a ladder of flexural beam modes (with five distinct resonance frequencies spanning from 3 to 208 MHz) within a nanocavity optomechanical torque sensor via magnetic hysteresis curves measured at mechanical resonances. At low DC fields the gyrotropic resonance of a magnetic vortex spin texture overlaps the 208 MHz mechanical mode. The massive EdH mechanical torques arising from this co-resonance yield a fingerprint of vortex core pinning and depinning in the sample. The experimental results are discussed in relation to mechanical torques predicted from both macrospin (at high DC magnetic field) and finite-difference solutions to the Landau-Lifshitz-Gilbert (LLG) equation. A global fit of the LLG solutions to the frequency-dependent data reveals a statistically significant discrepancy between the experimentally observed and simulated torque phase behaviours at spin texture transitions that can be reduced through the addition of a time constant to the conversion between magnetic cross-product torque and mechanical torque, constrained by experiment to be in the range of 0.5 - 4 ns.

Solid-that-flows picture of glass-forming liquids. (arXiv:2311.14460v3 [cond-mat.soft] UPDATED)
Jeppe C. Dyre

This perspective article reviews arguments that glass-forming liquids are different from those of standard liquid-state theory, which typically have a viscosity in the mPa$\cdot$s range and relaxation times of order picoseconds. These numbers grow dramatically and become $10^{12}-10^{15}$ times larger for liquids cooled toward the glass transition. This translates into a qualitative difference, and below the ``solidity length'' which is of order one micron at the glass transition, a glass-forming liquid behaves much like a solid. Recent numerical evidence for the solidity of ultraviscous liquids is reviewed, and experimental consequences are discussed in relation to dynamic heterogeneity, frequency-dependent linear-response functions, and the temperature dependence of the average relaxation time.

Non-equilibrium dynamics of electron emission from cold and hot graphene under proton irradiation. (arXiv:2311.18784v2 [cond-mat.mtrl-sci] UPDATED)
Yifan Yao, Alina Kononov, Arne Metzlaff, Andreas Wucher, Lukas Kalkhoff, Lars Breuer, Marika Schleberger, André Schleife

Characteristic properties of secondary electrons emitted from irradiated two-dimensional materials arise from multi-length and time-scale relaxation processes that connect the initial non-equilibrium excited electron distribution with their eventual emission. To understand these processes, which are critical for using secondary electrons as high-resolution thermalization probes, we combine first-principles real-time electron dynamics with modern experiments. Our data for cold and hot proton-irradiated graphene shows signatures of kinetic and potential emission and generally good agreement for electron yields between experiment and theory. The duration of the emission pulse is about 1.5 femtoseconds, indicating high time resolution when used as a probe. Our newly developed method to predict kinetic energy spectra shows good agreement with electron and ion irradiation experiments and prior models. We find that lattice temperature significantly increases secondary electron emission, whereas electron temperature has a negligible effect.

Current-induced near-field radiative energy, linear-momentum, and angular-momentum transfer. (arXiv:2312.07954v2 [physics.optics] UPDATED)
Huimin Zhu, Gaomin Tang, Lei Zhang, Jun Chen

In this work, we study the near-field radiative energy, linear-momentum, and angular-momentum transfer from a current-biased graphene to nanoparticles. The electric current through the graphene sheet induces nonequilibrium fluctuations, causing energy and momentum transfer even in the absence of a temperature difference. The inherent spin-momentum locking of graphene surface plasmons leads to an in-plane torque perpendicular to the direction of the electric current. In the presence of a temperature difference, the energy transfer is greatly enhanced while the lateral force and torque remains within the same order. Our work explores the potential of utilizing current-biased graphene to manipulate nanoparticles.

Real-space hole-doping titration and manipulation of correlated charge density wave state in 1T-TaS2. (arXiv:2401.01507v3 [cond-mat.str-el] UPDATED)
Haoyu Dong, Yanyan Geng, Jianfeng Guo, Le Lei, Yan Li, Li Huang, Fei Pang, Rui Xu, Weiqiang Yu, Wei Ji, Hong-Jun Gao, Weichang Zhou, Zhihai Cheng

The complex correlated charge density wave (CDW) phases of 1T-TaS2 have attracted great attention due to their emergent quantum states, such as intricate CDW phase, Mott-Hubbard state, superconductivity and quantum spin liquid. The delicate interplay among the complex intra-/inter-layer electron-electron and electron-lattice interactions is the fundamental prerequisite of these exotic quantum states. Here, we report a real-space titration-like investigation of correlated CDW state in 1T-TaS2 upon hole-doping via low-temperature scanning tunneling microscopy (LT-STM). The gradual increased hole-doping results in the sequential emergence of electron voids, phase domains, stacking disordering and mixed phase/chiral domains attributed to the reduced electron correlations. The achiral intermediate ring-like clusters and nematic CDW states emerge at the intralayer chiral domain wall and interlayer heterochiral stacking regions via the chiral-overlapping configurations. The local reversible CDW manipulation is further realized by the non-equilibrium transient charge-injections of STM field-emission spectra. Our results provide an in-depth insight of this intricate correlated CDW state, and pave a way to realize exotic quantum states via the accurate tuning of interior interactions in correlated materials.

High-topological-number skyrmions and phase transition in two-dimensional frustrated $J_1$-$J_2$ magnets. (arXiv:2401.05719v3 [physics.comp-ph] UPDATED)
Hongliang Hu, Zhong Shen, Zheng Chen, Xiaoping Wu, Tingting Zhong, Changsheng Song

With the rapidly expanded field of two-dimensional(2D) magnetic materials, the frustrated magnetic skyrmions are attracting growing interest recently. Here, based on hexagonal close-packed (HCP) lattice of $J_1$-$J_2$ Heisenberg spins model, we systematically investigate the frustrated skyrmions and phase transition by micromagnetic simulations and first-principles calculations. The results show that four spin phases of antiferromagnetic, labyrinth domain, skyrmion and ferromagnetic textures are determined by the identified ranges of $J_1$-$J_2$. Importantly, skyrmion phase with an increasing topological number ($Q$) covers a wider $J_1$-$J_2$ area. Then, the diameter of skyrmions can be tuned by the frustration strength ($|J_2/J_1|$) or external magnetic field. Besides, a phase transition from N$\acute{e}$el to Bloch type skyrmion is observed due to the change of the helicity with the variation of $|J_2/J_1|$. Furthermore, as increasing magnetic field, the skyrmions with high $Q$ ($\ge 3$) tend to split into the ones with $Q=1$, thereby achieving a lower systematic energy. Additionally, we find that the CoCl$_2$ monolayer satisfies the requirement of the frustrated $J_1$-$J_2$ magnet, and the related magnetic behaviors agree with the above conclusions. The frustration-induced skyrmions are stable without the manipulation of temperature and magnetic field. Our results may open a possible way toward spintronic applications based on High-topological-number and nanoscale topological spin textures of skyrmions.

Found 8 papers in prb
Date of feed: Tue, 23 Jan 2024 04:17:05 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)

Multiplicative topological semimetals
Adipta Pal, Joe H. Winter, and Ashley M. Cook
Author(s): Adipta Pal, Joe H. Winter, and Ashley M. Cook

Exhaustive study of topological semimetal (TSM) phases of matter in equilibriated electonic systems and myriad extensions has built upon the foundations laid by earlier introduction and study of Weyl semimetals, with broad applications in topologically protected quantum computing, spintronics, and o…

[Phys. Rev. B 109, 035147] Published Mon Jan 22, 2024

Higher-order double-Weyl semimetal
Baoru Pan, Yuzhong Hu, Pan Zhou, Huaping Xiao, Xuejuan Yang, and Lizhong Sun
Author(s): Baoru Pan, Yuzhong Hu, Pan Zhou, Huaping Xiao, Xuejuan Yang, and Lizhong Sun

Higher-order Weyl semimetal (HOWSM) is a fascinating topological phase that connects the nontrivial higher-order topology and Weyl semimetal. In this paper, we introduce a novel phase termed higher-order double-Weyl semimetals (HODWSMs) through the application of symmetry analysis and a minimal tigh…

[Phys. Rev. B 109, 035148] Published Mon Jan 22, 2024

Chern numbers for the two-body Hofstadter-Hubbard butterfly
D. C. Alyuruk and M. Iskin
Author(s): D. C. Alyuruk and M. Iskin

We analyze the two-body spectrum within the Hofstadter-Hubbard model on a square lattice through an exact variational ansatz and study the topological properties of its low-lying two-body bound-state branches. In particular, we discuss how the Hofstadter-Hubbard butterfly of the two-body branches ev…

[Phys. Rev. B 109, 035149] Published Mon Jan 22, 2024

Fermi surface nesting and topological and magnetoresistance properties of $\mathrm{Th}{X}_{2} (X=\mathrm{As},\mathrm{Sb},\mathrm{Bi})$
Sushree Sarita Sahoo, Ty M. Mason, Stephen B. Dugdale, and V. Kanchana
Author(s): Sushree Sarita Sahoo, Ty M. Mason, Stephen B. Dugdale, and V. Kanchana

In this constantly expanding and evolving era of advanced technology, there is great demand for a compound that boasts a plethora of exotic properties. To procure such a compound, we conducted a thorough analysis of the lattice and electronic properties of several Th-based compounds using first-prin…

[Phys. Rev. B 109, 035151] Published Mon Jan 22, 2024

Composite-fermion pairing at half-filled and quarter-filled lowest Landau level
Anirban Sharma, Ajit C. Balram, and J. K. Jain
Author(s): Anirban Sharma, Ajit C. Balram, and J. K. Jain

The physical origin of the fractional quantum Hall effect at the half-filled lowest Landau level in wide quantum wells has remained a puzzle since its discovery three decades ago. This work presents quantitative calculations supporting the formation of a p-wave topological “superconductor” of composite fermions (CFs) here. CFs are predicted to form f-wave pairs at the quarter-filled Landau level in wide quantum wells. CF pairing is thus seen as the principal mechanism underlying the even-denominator fractional quantum Hall effect.

[Phys. Rev. B 109, 035306] Published Mon Jan 22, 2024

Robust Majorana bound states in magnetic topological insulator nanoribbons with fragile chiral edge channels
Declan Burke, Dennis Heffels, Kristof Moors, Peter Schüffelgen, Detlev Grützmacher, and Malcolm R. Connolly
Author(s): Declan Burke, Dennis Heffels, Kristof Moors, Peter Schüffelgen, Detlev Grützmacher, and Malcolm R. Connolly

Magnetic topological insulators in the quantum anomalous Hall regime host ballistic chiral edge channels. When proximitized by an $s$-wave superconductor, these edge states offer the potential for realizing topological superconductivity and Majorana bound states without the detrimental effect of lar…

[Phys. Rev. B 109, 045138] Published Mon Jan 22, 2024

Quasiperiodic gallium adlayer on $i$-Al-Pd-Mn
Pramod Bhakuni, Marian Krajčí, and Sudipta Roy Barman
Author(s): Pramod Bhakuni, Marian Krajčí, and Sudipta Roy Barman

Using scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density functional theory (DFT), we demonstrate the formation of quasicrystalline gallium adlayer on icosahedral ($i$)-Al-Pd-Mn. Quasiperiodic motifs are evident in the STM topography images, including the Ga whit…

[Phys. Rev. B 109, 045427] Published Mon Jan 22, 2024

Simultaneous measurement of in-plane and interfacial thermal conductivity of isotopically labeled bilayer graphene
Yang Zhang, Qiancheng Ren, Jiayuan Fang, Jinglan Liu, Suhao Wang, Jizhou Song, and Pei Zhao
Author(s): Yang Zhang, Qiancheng Ren, Jiayuan Fang, Jinglan Liu, Suhao Wang, Jizhou Song, and Pei Zhao

The thermal properties of bilayer graphene (BLG) play a crucial role in the advancement of its promising electronic devices. However, the measurement of thermal conductivity using current techniques faces obstacles due to the low temperature gradient both in plane and across the interface in the sam…

[Phys. Rev. B 109, L041407] Published Mon Jan 22, 2024

Found 1 papers in prl
Date of feed: Tue, 23 Jan 2024 04:17:03 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)

Non-Abelian Topological Bound States in the Continuum
Long Qian, Weixuan Zhang, Houjuan Sun, and Xiangdong Zhang
Author(s): Long Qian, Weixuan Zhang, Houjuan Sun, and Xiangdong Zhang

Bound states in the continuum (BICs), which are spatially localized states with energies lying in the continuum of extended modes, have been widely investigated in both quantum and classical systems. Recently, the combination of topological band theory with BICs has led to the creation of topologica…

[Phys. Rev. Lett. 132, 046601] Published Mon Jan 22, 2024

Found 1 papers in pr_res
Date of feed: Tue, 23 Jan 2024 04:17:03 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)

Colloidal gelation induced by ring polymers
Esmaeel Moghimi, Iurii Chubak, Maria Kaliva, Parvin Kiany, Taihyun Chang, Junyoung Ahn, Nikolaos Patelis, Georgios Sakellariou, Sergei A. Egorov, Dimitris Vlassopoulos, and Christos N. Likos
Author(s): Esmaeel Moghimi, Iurii Chubak, Maria Kaliva, Parvin Kiany, Taihyun Chang, Junyoung Ahn, Nikolaos Patelis, Georgios Sakellariou, Sergei A. Egorov, Dimitris Vlassopoulos, and Christos N. Likos

When nonadsorbing ring polymers are added in a fluid suspension of big, spherical colloids, solid gels are formed. Joint experimental, computational, and theoretical work shows that these gels are much stronger than those formed by the addition of linear polymer chains.

[Phys. Rev. Research 6, 013079] Published Mon Jan 22, 2024

Found 1 papers in acs-nano
Date of feed: Mon, 22 Jan 2024 14:03:11 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)

[ASAP] Enhancing Solar-Driven Water Purification by Multiscale Biomimetic Evaporators Featuring Lamellar MoS2/GO Heterojunctions
Haotian Zheng, Jiahui Fan, Aiying Chen, Xiang Li, Xiaofeng Xie, Yong Liu, and Zhiyi Ding

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c08648

Found 3 papers in comm-phys

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)

Strain-tunable Dirac semimetal phase transition and emergent superconductivity in a borophane
Peng Yu

Communications Physics, Published online: 20 January 2024; doi:10.1038/s42005-024-01523-x

The reduced dimensions of 2D materials increase the strength of electron-electron correlations and hence they can be used as a platform to engineer exotic physical states such as Dirac semimetals. Here, using first-principles calculations, the authors investigate the mechanical properties of β12-B5H3, as well as possible Dirac semimetal and phonon-mediated superconducting phases.

Metasurface-based perfect vortex beam for optical eraser
Shao-Yang Huang

Communications Physics, Published online: 17 January 2024; doi:10.1038/s42005-024-01525-9

In this work, metasurface-based perfect vortex beams (MPVBs) featuring topological charges (TCs) of −32 and 16 have been successfully manufactured. As one of the tremendous phenomena in quantum mechanics, the fancy optical eraser experiment by integrating these MPVBs has also been successfully demonstrated in this study.

Observation of large spin-polarized Fermi surface of a magnetically proximitized semiconductor quantum well
Masaaki Tanaka

Communications Physics, Published online: 15 January 2024; doi:10.1038/s42005-023-01485-6

Narrow-gap semiconductors with gate-controllable spin-splitting provide an ideal platform for novel spintronic and topological devices. The authors observe a large spontaneous spin-splitting energy, reaching 18 meV and widely tunable by a gate voltage, in an InAs quantum well that is magnetically proximitized by a ferromagnetic semiconductor (Ga,Fe)Sb.