Found 62 papers in cond-mat

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Bipartite Fluctuations of Critical Fermi Surfaces
Xiao-Chuan Wu
arXiv:2404.04331v1 Announce Type: new Abstract: We investigate the scaling behaviors of bipartite fluctuations $\mathcal{F}$ of conserved quantities across a class of interaction-driven quantum phase transitions out of Landau fermi liquids, where other phases involve fermi-surface states of fractionalized degrees of freedom. Examples of such phases include (compressible) composite fermi liquids for spinless electrons and (incompressible) spin-liquid Mott insulators for spin-$1/2$ electrons. The two sides of the critical points are typically distinguished by distinct leading-order scalings of bipartite charge fluctuations, $\mathcal{F}\sim L\log (L)$ in Landau fermi liquids, and $\mathcal{F}\sim L$ in the other phases, where $L$ is the linear size of the subsystem under bipartition. In the case of composite fermi liquids (with continuous translational and rotational invariance), we also identify a universal constant term $-\mathtt{F}(\theta)\sigma_{xy}/\pi$ arising when the subsystem geometry incorporates a sharp corner. Here, $\mathtt{F}(\theta)$ represents a function of the corner angle, and $\sigma_{xy}$ denotes the Hall conductivity. At the critical point of each example, we find that the leading-order scaling $\mathcal{F}\sim L$ is accompanied by a subleading universal corner contribution $-\mathtt{F}(\theta)C_{\rho}\log(L)$ with the same angle dependence $\mathtt{F}(\theta)$. The universal coefficient $C_{\rho}$ is linked to the predicted universal longitudinal (and Hall) resistivity jump $\Delta\rho_{xx}$ (and $\Delta\rho_{xy}$) at the critical point.

Disorder operators in 2D Fermi and non-Fermi liquids through multidimensional bosonization
Kang-Le Cai, Meng Cheng
arXiv:2404.04334v1 Announce Type: new Abstract: Disorder operators are a type of non-local observables for quantum many-body systems, measuring the fluctuations of symmetry charges inside a region. It has been shown that disorder operators can reveal global aspects of many-body states that are otherwise difficult to access through local measurements. We study disorder operator for U(1) (charge or spin) symmetry in 2D Fermi and non-Fermi liquid states, using the multidimensional bosonization formalism. For a region $A$, the logarithm of the charge disorder parameter in a Fermi liquid with isotropic interactions scales asympototically as $l_A\ln l_A$, with $l_A$ being the linear size of the region $A$. We calculate the proportionality coefficient in terms of Landau parameters of the Fermi liquid theory. We then study models of Fermi surface coupled to gapless bosonic fields realizing non-Fermi liquid states. In a simple spinless model, where the fermion density is coupled to a critical scalar, we find that at the quantum critical point, the scaling behavior of the charge disorder operators is drastically modified to $l_A \ln^2 l_A$. We also consider the composite Fermi liquid state and argue that the charge disorder operator scales as $l_A$.

Possible charge density wave induced lattice distortion in ferromagnetic FeGe film
Guangdong Nie, Guanghui Han, Erfa S. Z., Shijian Chen, Hao Ding, Fangdong Tang, Licong Peng, Young Sun, Deshun Hong
arXiv:2404.04480v1 Announce Type: new Abstract: Binary compound FeGe hosts multiple structures, where skyrmion lattice emerges in the chiral B20 phase and antiferromagnet with charge density wave shows up in the hexagonal phase. Here, we synthesized monoclinic FeGe films which are ferromagnetic with Curie temperature as high as 800 K. By low temperature transmission electron microscope, lattice reconstructions in both real and reciprocal space were captured at 100 K whereas no observable transition was observed in either transport nor magnetic characterizations. We infer the lattice distortion may be induced by charge density wave. Our work suggests FeGe films an ideal platform for understanding the intertwining of charge density wave, lattice distortion and magnetism, and paves the way to the tuning charge density wave by means of lattice engineering.

Theory of local $\mathbb{Z}_{2}$ topological markers for finite and periodic two-dimensional systems
Nicolas Ba\`u, Antimo Marrazzo
arXiv:2404.04598v1 Announce Type: new Abstract: The topological phases of two-dimensional time-reversal symmetric insulators are classified by a $\mathbb{Z}_{2}$ topological invariant. Usually, the invariant is introduced and calculated by exploiting the way time-reversal symmetry acts in reciprocal space, hence implicitly assuming periodicity and homogeneity. Here, we introduce two space-resolved $\mathbb{Z}_{2}$ topological markers that are able to probe the local topology of the ground-state electronic structure also in the case of inhomogeneous and finite systems. The first approach leads to a generalized local spin-Chern marker, that usually remains well-defined also when the perpendicular component of the spin, $S_{z}$, is not conserved. The second marker is solely based on time-reversal symmetry, hence being more general. We validate our markers on the Kane-Mele model both in periodic and open boundary conditions, also in presence of disorder and including topological/trivial heterojunctions.

Quantized perfect transmission in graphene nanoribbons with random hollow adsorbates
Jia-Le Yu, Zhe Hou, Irfan Hussain Bhat, Pei-Jia Hu, Jia-Wen Sun, Xiao-Feng Chen, Ai-Min Guo, Qing-Feng Sun
arXiv:2404.04607v1 Announce Type: new Abstract: Impurities exist inevitably in two-dimensional materials as they spontaneously adsorb onto the surface during fabrication, usually exerting detrimental effects on electronic transport. Here, we focus on a special type of impurities that preferentially adsorb onto the hollow regions of graphene nanoribbons (GNRs), and study how they affect the quantum transport in GNRs. Contrary to previous knowledge that random adatoms should localize electrons, the so-called Anderson localization, noteworthy quantized conductance peaks (QCPs) are observed at specific electron energies. These QCPs are remarkably robust against variations in system size, GNR edge, and adatom properties, and they can reappear at identical energies following an arithmetic sequence of device width. Further investigation of wavefunction reveals a unique transport mode at each QCP energy which transmits through disordered GNRs reflectionlessly, while all the others become fully Anderson localized, indicating the survival of quantum ballistic transport in the localized regime. Our findings highlight the potential utility of hollow adatoms as a powerful tool to manipulate the conductivity of GNRs, and deepen the understanding of the interplay between impurities and graphene.

Phases, morphologies, and transitions in a membrane model for the endoplasmic reticulum
Jaya Kumar Alageshan, Yashodhan Hatwalne, Rahul Pandit
arXiv:2404.04611v1 Announce Type: new Abstract: We introduce a novel model, comprising self-avoiding surfaces and incorporating edges and tubules, that is designed to characterize the structural morphologies and transitions observed within the endoplasmic reticulum (ER). By employing discretized models, we model smooth membranes with triangulated surfaces, and we utilize numerical variational methods to minimize energies associated with periodic morphologies. Our study obtains phases, their morphologies, and their transitions and examines their dependence on the membrane chemical potential, the line tensions, and the positive Gaussian curvature stiffness. By starting with diverse topological structures, we explore shape variations by using Surface Evolver, while maintaining fixed topology. Notably, we identify the region of parameter space where the model displays lamellae, with a lattice of helical edges connecting the layers; this resembles structures that have been observed in the rough ER. Furthermore, our investigation reveals an intricate phase diagram with periodic structures, including flat lamellar sheets, sponge phases, and configurations comprising tubules with junctions, which are akin to the morphology of the smooth ER. An estimation of lattice parameters is achieved through fluctuation analysis. Significantly, our model predicts a transition between homotopically equivalent lamellae, with helical edges and configurations featuring tubules with junctions.

Flat-Band Enhanced Antiferromagnetic Fluctuations and Unconventional Superconductivity in Pressurized CsCr$_3$Sb$_5$
Siqi Wu, Chenchao Xu, Xiaoqun Wang, Hai-Qing Lin, Chao Cao, Guang-Han Cao
arXiv:2404.04701v1 Announce Type: new Abstract: The interrelationship between flat bands and correlated phenomena such as unconventional superconductivity stands as an intriguing subject in condensed matter physics. Here, by first-principles calculations and random phase approximation analyses, we investigate the electronic structure, superconducting instability, as well as roles of the incipient flat bands in kagome superconductor CsCr$_3$Sb$_5$. Our calculations reveal strong antiferromagnetic spin fluctuations in CsCr$_3$Sb$_5$, which mediates two sets of spin-singlet superconducting orders with $s_{\pm}$- and ($d_{xy}$, $d_{x^2-y^2}$)-wave symmetries. Under the dominance of local Coulomb interactions, the unoccupied incipient flat bands are shown to be crucial for the momentum dependence of spin fluctuations and thus the superconductivity. Our further analyses unveil a sublattice-momentum-coupling-driven mechanism for this momentum-dependent enhancement of the fluctuations, which provides us a new perspective for future studies of geometrically frustrated systems.

Magneto-Induced Topological Phase Transition in Inverted InAs/GaSb Bilayers
Zhongdong Han, Tingxin Li, Long Zhang, Rui-Rui Du
arXiv:2404.04830v1 Announce Type: new Abstract: We report a magneto-induced topological phase transition in inverted InAs/GaSb bilayers from a quantum spin Hall insulator to a normal insulator. We utilize a dual-gated Corbino device in which the degree of band inversion, or equivalently the electron and hole densities, can be continuously tuned. We observe a topological phase transition around the magnetic field where a band crossing occurs, that is accompanied by a bulk-gap closure characterized by a bulk conductance peak (BCP). In another set of experiments, we study the transition under a tilted magnetic field (tilt angle $\theta$). We observe the characteristic magneto-conductance around BCP as a function of $\theta$, which dramatically depends on the density of the bilayers. In a relatively deep-inversion (hence a higher density) regime, where the electron-hole hybridization dominates the excitonic interaction, the BCP grows with $\theta$. On the contrary, in a shallowly-inverted (a lower density) regime, where the excitonic interaction dominates the hybridization, the BCP is suppressed indicating a smooth crossover without a gap closure. This suggests the existence of a low-density, correlated insulator with spontaneous symmetry breaking near the critical point. Our highly controllable electron-hole system offers an ideal platform to study interacting topological states as proposed by recent theories.

Site-ordering/disordering-induced magnetic textures in a vdW ferromagnet by competing global and broken inversion-symmetry
Haoyan Zhang, Jianfeng Guo, Cong Wang, Le Lei, Shuo Mi, Songyang Li, Congkuan Tian, Shaohua Yan, Hanxiang Wu, Shiyu Zhu, Rui Xu, Xueyun Wang, Hechang Lei, Peng Cheng, Fei Pang, Wei Ji, Zhihai Cheng
arXiv:2404.04851v1 Announce Type: new Abstract: Fe5GeTe2 single crystals can be divided into nonquenched (NQ) and quench-cooled (QC) phases with different magnetic properties. A comprehensive understanding of the magnetic property variations in the NQ and QC phases is imperative for guiding Fe5GeTe2 towards spintronics applications; however, it remains elusive. Here, we report a real-space study on the structural and magnetic properties of these two magnetic phases using cryogenic magnetic force microscopy and scanning tunneling microscopy. The thermal history introduces disorder and order to the Fe(1) sites, resulting in the NQ and QC phases exhibiting global and broken inversion symmetry, respectively. The observed magnetic domain transitions (branching to labyrinthine) in the spin reorientation process and the distinct 3D spin textures stabilized by magnetic dipolar interaction observed in field-dependent studies allow the NQ phase to exhibit a more resilient global magnetic state. In contrast, the QC phase exhibits enhanced magnetic anisotropy, resulting in a higher TC. Meanwhile, the Dzyaloshinskii-Moriya interaction (DMI) introduced by the broken inversion symmetry causes the QC phase to exhibit a localized magnetic state: no domain transformation occurs during spin reorientation, and irregular domain states are observed in field-related studies. Our work provides an important reference for understanding the complex magnetic properties in Fe5GeTe2.

Optical absorption window in Na$_3$Bi based three-dimensional Dirac electronic system
Q. N. Li, W. Xu, Y. M. Xiao, L. Ding, B. Van Duppen, F. M. Peeters
arXiv:2404.04888v1 Announce Type: new Abstract: We present a detailed theoretical study of the optoelectronic properties of a Na$_3$Bi-based three-dimensional Dirac electronic system (3DDES). The optical conductivity is evaluated using the energy-balance equation derived from a Boltzmann equation, where the electron Hamiltonian is taken from a simplified $\mathbf{k}\cdotp \mathbf{p}$ approach. We find that for short-wavelength irradiation, the optical absorption in Na$_3$Bi is mainly due to inter-band electronic transitions. In contrast to the universal optical conductance observed for graphene, the optical conductivity for Na$_3$Bi based 3DDES depends on the radiation frequency but not on temperature, carrier density and electronic relaxation time. In the radiation wavelength regime of about 5 $\mu m<\lambda<$ 200 $\mu m$, an optical absorption window is found. This is similar to what is observed in graphene. The position and width of the absorption window depend on the direction of the light polarization and sensitively on temperature, carrier density, and electronic relaxation time. Particularly, we demonstrate that the inter-band optical absorption channel can be switched on and off by applying the gate voltage. This implies that similar to graphene, Na$_3$Bi based 3DDES can also be applied in infrared electro-optical modulators. Our theoretical findings are helpful in gaining an in-depth understanding of the basic optoelectronic properties of recently discovered 3DDESs.

Linear differential equation approach to the Loschmidt amplitude
Michael Vogl
arXiv:2404.04921v1 Announce Type: new Abstract: The Loschmidt echo is a popular quantity that allows making predictions about the stability of quantum states under time evolution. In our work, we present an approach that allows us to find a differential equation that can be used to compute the Loschmidt echo. This approach, while in essence perturbative, has the advantage that it converges at finite order. We demonstrate that the approach for generically chosen matrix Hamiltonians often offers advantages over Taylor and cumulant expansions even when we truncate at finite order. We then apply the approach to two ordinary band Hamiltonians (multi-Weyl semimetals and AB bilayer graphene) to obtain the Loschmidt echo after a quench for an arbitrary starting state and find that the results readily generalize to find transmission amplitudes and specific contributions to the partition function, too. We then test our methods on many body spin and fermionic Hamiltonians and find that while the approach still offers advantages, more care has to be taken than in a generic case.

Cryogen-free modular scanning tunneling microscope operating at 4-K in high magnetic field on a compact ultra-high vacuum platform
Angela M. Coe, Guohong Li, Eva Y. Andrei
arXiv:2404.05002v1 Announce Type: new Abstract: One of the daunting challenges in modern low temperature scanning tunneling microscopy (STM) is the difficulty of combining atomic resolution with cryogen free cooling. Further functionality needs, such as ultra-high vacuum (UHV), high magnetic field, and compatibility with {\mu}m-sized samples, pose additional challenges to an already ambitious build. We present the design, construction, and performance of a cryogen free, UHV, low temperature, and high magnetic field system for modular STM operation. An internal vibration isolator reduces vibrations in this system allowing atomic resolution STM imaging while maintaining a low base temperature of ~4K and magnetic fields up to 9T. Samples and tips can be conditioned in-situ utilizing a heating stage, an ion sputtering gun, an e-beam evaporator, a tip treater, and sample exfoliation. In-situ sample and tip exchange and alignment are performed in a connected UHV room temperature stage with optical access. Multisite operation without breaking vacuum is enabled by a unique quick-connect STM head design. A novel low-profile vertical transfer mechanism permits transferring the STM between room temperature and the low temperature cryostat.

Near-critical dark opalescence in out-of-equilibrium SF$_6$
Valentina Martelli, Amaury Anquetil, Lin Al Atik, J. Larrea Jim\'enez, Alaska Subedi, Ricardo P. S. M. Lobo, Kamran Behnia
arXiv:2404.05005v1 Announce Type: new Abstract: The first-order phase transition between the liquid and gaseous phases ends at a critical point. Critical opalescence occurs at this singularity. Discovered in 1822, it is known to be driven by diverging fluctuations in the density. During the past two decades, boundaries between the gas-like and liquid-like regimes have been theoretically proposed and experimentally explored. Here, we show that fast cooling of near-critical sulfur hexafluoride (SF$_6$), in presence of Earth's gravity, favors dark opalescence, where visible photons are not merely scattered, but also absorbed. When the isochore fluid is quenched across the critical point, its optical transmittance drops by more than three orders of magnitude in the whole visible range, a feature which does not occur during slow cooling. We show that transmittance shows a dip at 2eV near the critical point, and the system can host excitons with binding energies ranging from 0.5 to 4 eV. The spinodal decomposition of the liquid-gas mixture, by inducing a periodical modulation of the fluid density, can provide a scenario to explain the emergence of this platform for coupling between light and matter. The possible formation of excitons and polaritons points to the irruption of quantum effects in a quintessentially classical context.

Inducing a Metal-Insulator Transition through Systematic Alterations of Local Rewriting Rules in a Quantum Graph
Richard Berkovits
arXiv:2404.05013v1 Announce Type: new Abstract: The Anderson localization transition in quantum graphs has garnered significant recent attention due to its relevance to many-body localization studies. Typically, graphs are constructed using top-down methods. Here, we explore a bottom-up approach, employing a simple local rewriting rule to construct the graph. Through the use of ratio statistics for the energy spectrum and Kullback-Leibler divergence correlations for the eigenstates, numerical analysis demonstrates that slight adjustments to the rewriting rule can induce a transition from a localized to an extended quantum phase. This extended state exhibits non-ergodic behavior, akin to the non-ergodic extended phase observed in the Porter-Rosenzweig model and suggested for many-body localization. Thus, by adapting straightforward local rewriting rules, it becomes feasible to assemble complex graphs from which desired global quantum phases emerge. This approach holds promise for numerical investigations and could be implemented in building optical realizations of complex networks using optical fibers and beam splitters.

Effect of nonlocal interlayer hopping on wave function in twisted bilayer graphene
Hridis K. Pal
arXiv:2404.05025v1 Announce Type: new Abstract: The conventional low-energy theory employed to describe twisted bilayer graphene (TBG) relies on a local interlayer Hamiltonian. According to this theory, TBG has the same linear-in-momentum dispersion and spinor wave function at the Dirac point as single-layer graphene (SLG), albeit with a renormalized velocity that decreases as the rotation angle between the layers decreases, eventually reaching zero at the magic angle. In this work, I expand upon this low-energy theory by including nonlocal terms in the interlayer part of the Hamiltonian, and explore the consequences at the Dirac point. It is found that the nonlocality predominantly influences the wave function rather than the energy spectrum: despite the persistence of the linear-in-momentum dispersion with a renormalized velocity, the wave functions no longer mirror those of SLG. Instead, an additional contribution to the phase difference between the sublattice components of the spinor emerges. This gives rise to interesting effects in scattering which are demonstrated with a simple example.

Probing the Anisotropic Fermi Surface in Tetralayer Graphene via Transverse Magnetic Focusing
Illias Klanurak, Kenji Watanabe, Takashi Taniguchi, Sojiphong Chatraphorn, Thiti Taychatanapat
arXiv:2404.05038v1 Announce Type: new Abstract: Bernal-stacked tetralayer graphene (4LG) exhibits intriguing low-energy properties, featuring two massive subbands and showcasing diverse features of topologically distinct, anisotropic Fermi surfaces, including Lifshitz transitions and trigonal warping. Here, we study the influence of the band structure on electron dynamics within 4LG using transverse magnetic focusing. Our analysis reveals two distinct focusing peaks corresponding to the two subbands. Furthermore, we uncover a pronounced dependence of the focusing spectra on crystal orientations, indicative of an anisotropic Fermi surface. Utilizing the semiclassical model, we attribute this orientation-dependent behavior to the trigonal warping of the band structure. This phenomenon leads to variations in electron trajectories based on crystal orientation. Our findings not only enhance our understanding of the dynamics of electrons in 4LG, but also offer a promising method for probing anisotropic Fermi surfaces in other materials.

Moir\'e superlattices of antimonene on a Bi(111) substrate with van Hove singularity and Rashba-type spin polarization
Tomonori Nakamura, Yitao Chen, Ryohei Nemoto, Wenxuan Qian, Yuto Fukushima, Kaishu Kawaguchi, Ryo Mori, Takeshi Kondo, Youhei Yamaji, Shunsuke Tsuda, Koichiro Yaji, Takashi Uchihashi
arXiv:2404.05142v1 Announce Type: new Abstract: Moir\'e superlattices consisting of two-dimensional (2D) materials have attracted immense attention because of emergent phenomena such as flat band-induced Mott insulating states and unconventional superconductivity. However, the effects of spin-orbit coupling (SOC) on them have not been fully explored yet. Here we show that single- and double-bilayer (BL) Sb honeycomb lattices, referred to as antimonene, forms moir\'e superlattices on a Bi(111) substrate due to a lattice mismatch. Scanning tunnelling microscopy (STM) measurements reveal the presence of spectral peaks near the Fermi level, which are spatially modulated with the moir\'e period. Angle-resolved photoemission spectroscopy (ARPES) combined with density functional theory (DFT) calculations clarifies the surface band structure with saddle points near the Fermi level, which allows us to attribute the observed STM spectral peaks to the van Hove singularity. Spin-resolved ARPES measurements also shows that the observed surface states are Rashba-type spin-polarized. The present work has significant implications that Fermi surface instability and symmetry breaking may emerge at low temperatures, where spin degree of freedom and electron correlation will also play important roles.

Probing Plexciton Emission from 2D Materials on Gold Nanotrenches
Junze Zhou, P. A. D. Gon\c{c}alves, Fabrizio Riminucci, Scott Dhuey, Edward Barnard, Adam Schwartzberg, F. Javier Garc\'ia de Abajo, Alexander Weber-Bargioni
arXiv:2404.05161v1 Announce Type: new Abstract: Probing strongly coupled quasiparticle excitations at their intrinsic length scales offers unique insights into their properties and facilitates the design of devices with novel functionalities. In this work, we investigate the formation and emission characteristics of plexcitons, arising from the interaction between surface plasmons in narrow gold nanotrenches and excitons in monolayer WSe2. We study this strong plasmon-exciton coupling in both the far-field and the near-field. Specifically, we observe a Rabi splitting in the far-field reflection spectra of about 80 meV under ambient conditions, consistent with our theoretical modeling. Using a custom-designed near-field probe, we find that plexciton emission originates predominantly from the lower-frequency branch, which we can directly probe and map the local field distribution. We precisely determine the plexciton extension, similar to the trench width, with nanometric precision via collecting spectra at controlled probe locations. Our work opens exciting prospects for nanoscale mapping and engineering of plexcitons in complex nanostructures with potential applications in nanophotonic devices, optoelectronics, and quantum electrodynamics in nanoscale cavities.

Effect of collective spin excitation on electronic transport in topological spin texture
Kohei Hattori, Hikaru Watanabe, Junta Iguchi, Takuya Nomoto, Ryotaro Arita
arXiv:2404.05204v1 Announce Type: new Abstract: We develop an efficient real-time simulation method for the spin-charge coupled system in the velocity gauge. This method enables us to compute the real-time simulation for the two-dimensional system with the complex spin texture. We focus on the effect of the collective excitation of the localized spins on the electronic transport properties of the non-trivial topological state in real space. To investigate this effect, we calculate the linear optical conductivity by calculating the real-time evolution of the Kondo lattice model on the triangular lattice, which hosts an all-in/all-out magnetic structure. In the linear conductivity spectra, we observe multiple peaks below the bandgap regime, attributed to the resonant contributions of collective modes similar to the skyrmionic system, alongside broadband modifications resulting from off-resonant spin dynamics. The result shows that the collective excitation, similar to the skyrmionic system, influences the optical response of the electron systems based on symmetry analysis. We elucidate the interference between the contributions from the different spin excitations to the optical conductivity in the multiple spin texture, pointing out the mode-dependent electrical activity. We show the complex interplay between the complex spin texture and the itinerant electrons in the two-dimensional spin-charge coupled system.

Optical spin orientation of localized electrons and holes interacting with nuclei in an FA0.9Cs0.1PbI2.8Br0.2 perovskite crystal
Dennis Kudlacik, Nataliia E. Kopteva, Mladen Kotur, Dmitri R. Yakovlev, Kirill V. Kavokin, Carolin Harkort, Marek Karzel, Evgeny A. Zhukov, Eiko Evers, Vasilii V. Belykh, Manfred Bayer
arXiv:2404.05369v1 Announce Type: new Abstract: Optical orientation of carrier spins by circularly polarized light is the basic concept and tool of spin physics in semiconductors. We study the optical orientation of electrons and holes in a crystal of the FA$_{0.9}$Cs$_{0.1}$PbI$_{2.8}$Br$_{0.2}$ lead halide perovskite by means of polarized photoluminescence, time-resolved differential reflectivity, and time-resolved Kerr rotation. At the cryogenic temperature of 1.6 K the optical orientation degree measured for continuous-wave excitaton reaches 6\% for localized electrons and 2\% for localized holes. Their contributions are distinguished from each other and from exciton optical orientation through the pronounced Hanle effect in transverse magnetic fields and the polarization recovery effect in longitudinal magnetic fields. The optical orientation degree is highly stable against detuning of the laser photon energy from the band gap by up to 0.25 eV, showing then a gradual decrease for detunings up to 0.9 eV. This evidences the inefficiency of spin relaxation mechanisms for free carriers during their energy relaxation. Spin relaxation for localized electrons and holes is provided by the hyperfine interaction with the nuclear spins. Dynamic polarization of nuclear spins is demonstrated by the Overhauser field reaching 4 mT acting on the electrons and $-76$ mT acting on the holes. This confirms the specifics of lead halide perovskite semiconductors, where the hole hyperfine interaction with the nuclei considerably exceeds that of the electron.

Multiple Floquet Chern insulator phases in the spin-charge coupled triangular-lattice ferrimagnet: Crucial roles of higher-order terms in the high-frequency expansion
Rintaro Eto, Masahito Mochizuki
arXiv:2404.05385v1 Announce Type: new Abstract: We study the effects of photoirradiation with circularly polarized light on the Dirac half-metal state induced by the ferrimagnetic order in a triangular Kondo-lattice model. Our analysis based on the Floquet theory reveals that two types of Floquet Chern insulator phases appear as photoinduced nonequilibrium steady states and that these two phases can be experimentally detected and distinguished by measurements of the Hall conductivity. It is elucidated that these rich nonequilibrium topological phases come from higher-order terms in the high-frequency expansion called Brillouin-Wigner expansion, which is in striking contrast to usually discussed Floquet Chern insulator phases originating from the lowest-order terms of the expansion. So far, the lattice electron models on simple non-multipartite lattices such as triangular lattices and square lattices have not been regarded as targets of the Floquet engineering because the lowest-order terms of the high-frequency expansion for Floquet effective Hamiltonians cancel each other to vanish in these systems. Our findings of the Floquet Chern insulator phases in a triangular Kondo-lattice model are expected to expand the range of potential models and even materials targeted by the Floquet engineering.

An Oedometer Test under Acid Injection with a Discrete Element Model: the case of Debonding
Alexandre Sac-Morane, Hadrien Rattez, Manolis Veveakis
arXiv:2404.05390v1 Announce Type: new Abstract: Rock weathering is a common phenomenon in most engineering applications, such as underground storage or geothermal energy. This work offers a discrete element modelization of the problem considering cohesive granular material and debonding effect. Oedometer conditions are applied during the weathering and the evolution of the coefficient of lateral earth pressure, a proxy of the state of stress, is tracked. Especially, the influence of the degree of cementation, the confining pressure, the initial value of k0 and the history of load are investigated. It has been emphasized that the granular media aims to reach an attractor configuration. And the grain reorganization occurring is divided into two main phenomena: the collapse of the unstable chain forces (stable only thanks to the cementation) and the softening of the grains.

Valley edge states as bound states in the continuum
Shunda Yin, Liping Ye, Hailong He, Xueqin Huang, Manzhu Ke, Weiyin Deng, Jiuyang Lu, Zhengyou Liu
arXiv:2404.05412v1 Announce Type: new Abstract: Bound states in the continuum (BICs) are spatially localized states with energy embedded in the continuum spectrum of extended states. The combination of BICs physics and nontrivial band topology theory giving rise to topological BICs, which are robust against disorders and meanwhile of the merit of conventional BICs, is attracting wide attention recently. Here, we report valley edge states as topological BICs, which appear at domain wall between two distinct valley topological phases. The robustness of such BICs is demonstrated. The simulations and experiments show great agreement. Our findings of valley related topological BICs shed light on both BICs and valley physics, and may foster innovative applications of topological acoustic devices.

An intriguing connection between the Bardeen-Moshe-Bander phenomenon and 2+p spin glasses
Vincent Lahoche, Dine Ousmane Samary
arXiv:2404.05436v1 Announce Type: new Abstract: This paper aims to establish a close connection between the Bardeen-Moshe-Bander phenomenon and a p=2+3 spin-glass model with sextic confinement potential. This is made possible by the unconventional power-counting induced by the effective kinetics provided by the disorder coupling in the large $N$-limit. Because of the absence of epsilon expansion, our approach is more attractive than the previous one and plays a relevant role in the signal detection issue in nearly continuous spectra.

SrRuO3 under tensile strain: Thickness-dependent electronic and magnetic properties
Yuki K. Wakabayashi, Masaki Kobayashi, Yuichi Seki, Kohei Yamagami, Takahito Takeda, Takuo Ohkochi, Yoshitaka Taniyasu, Yoshiharu Krockenberger, Hideki Yamamoto
arXiv:2404.05438v1 Announce Type: new Abstract: The burgeoning fields of spintronics and topological electronics require materials possessing a unique combination of properties: ferromagnetism, metallicity, and chemical stability. SrRuO3 (SRO) stands out as a compelling candidate due to its exceptional combination of these attributes. However, understanding its behavior under tensile strain, especially its thickness-dependent changes, remains elusive. This study employs machine-learning-assisted molecular beam epitaxy to investigate SRO films with thicknesses from 1 to 10 nm. This work complements the existing focus on compressive-strained SRO, opening a new avenue for exploring its hitherto concealed potential. Using soft X-ray magnetic circular dichroism, we uncover an intriguing interplay between film thickness, electronic structure, and magnetic properties. Our key findings reveal an intensified localization of Ru 4d t2g-O 2p hybridized states at lower thicknesses, attributed to the weakened orbital hybridization. Furthermore, we find a progressive reduction of magnetic moments for both Ru and O ions as film thickness decreases. Notably, a non-ferromagnetic insulating state emerges at a critical thickness of 1 nm, marking a pivotal transition from the metallic ferromagnetic phase. These insights emphasize the importance of considering thickness-dependent properties when tailoring SRO for next-generation spintronic and topological electronic devices.

Implementation of the bilayer Hubbard model in a moir\'e heterostructure
Borislav Polovnikov, Johannes Scherzer, Subhradeep Misra, Henning Schl\"omer, Julian Trapp, Xin Huang, Christian Mohl, Zhijie Li, Jonas G\"oser, Jonathan F\"orste, Ismail Bilgin, Kenji Watanabe, Takashi Taniguchi, Annabelle Bohrdt, Fabian Grusdt, Anvar S. Baimuratov, Alexander H\"ogele
arXiv:2404.05494v1 Announce Type: new Abstract: Moir\'e materials provide a unique platform for studies of correlated many-body physics of the Fermi-Hubbard model on triangular spin-charge lattices. Bilayer Hubbard models are of particular significance with regard to the physics of Mott insulating states and their relation to unconventional superconductivity, yet their experimental implementation in moir\'e systems has so far remained elusive. Here, we demonstrate the realization of a staggered bilayer triangular lattice of electrons in an antiparallel MoSe$_{2}$/WS$_{2}$ heterostructure. The bilayer lattice emerges due to strong electron confinement in the moir\'e potential minima and the near-resonant alignment of conduction band edges in MoSe$_{2}$ and WS$_{2}$. As a result, charge filling proceeds layer-by-layer, with the first and second electron per moir\'e cell consecutively occupying first the MoSe$_{2}$ and then the WS$_{2}$ layer. We describe the observed charging sequence by an electrostatic model and provide experimental evidence of spin correlations on the vertically offset and laterally staggered bilayer lattice, yielding absolute exciton Land\'e factors as high as $600$ at lowest temperatures. The bilayer character of the implemented spin-charge lattice allows for electrostatic tunability of Ruderman-Kittel-Kasuya-Yosida magnetism, and establishes antiparallel MoSe$_{2}$/WS$_{2}$ heterostructures as a viable platform for studies of bilayer Hubbard model physics with exotic magnetic phases on frustrated lattices.

Observation of dichotomic field-tunable electronic structure in twisted monolayer-bilayer graphene
Hongyun Zhang, Qian Li, Youngju Park, Yujin Jia, Wanying Chen, Jiaheng Li, Qinxin Liu, Changhua Bao, Nicolas Leconte, Shaohua Zhou, Yuan Wang, Kenji Watanabe, Takashi Taniguchi, Jose Avila, Pavel Dudin, Pu Yu, Hongming Weng, Wenhui Duan, Quansheng Wu, Jeil Jung, Shuyun Zhou
arXiv:2404.05533v1 Announce Type: new Abstract: Twisted bilayer graphene (tBLG) provides a fascinating platform for engineering flat bands and inducing correlated phenomena. By designing the stacking architecture of graphene layers, twisted multilayer graphene can exhibit different symmetries with rich tunability. For example, in twisted monolayer-bilayer graphene (tMBG) which breaks the C2z symmetry, transport measurements reveal an asymmetric phase diagram under an out-of-plane electric field, exhibiting correlated insulating state and ferromagnetic state respectively when reversing the field direction. Revealing how the electronic structure evolves with electric field is critical for providing a better understanding of such asymmetric field-tunable properties. Here we report the experimental observation of field-tunable dichotomic electronic structure of tMBG by nanospot angle-resolved photoemission spectroscopy (NanoARPES) with operando gating. Interestingly, selective enhancement of the relative spectral weight contributions from monolayer and bilayer graphene is observed when switching the polarity of the bias voltage. Combining experimental results with theoretical calculations, the origin of such field-tunable electronic structure, resembling either tBLG or twisted double-bilayer graphene (tDBG), is attributed to the selectively enhanced contribution from different stacking graphene layers with a strong electron-hole asymmetry. Our work provides electronic structure insights for understanding the rich field-tunable physics of tMBG.

Towards an understanding of particle-scale flaws and microstructure evolution in cold-spray via accumulation of single particle impacts
Alain Reiser, Christopher Allan Schuh
arXiv:2404.05601v1 Announce Type: new Abstract: Cold spray coatings are the sum of countless individual bonding events between single particles impacting on top of one another at high velocities. Thus, the collective behavior of microparticles must be considered to elucidate the origins of coating flaws at the scale of the particles and larger, or the dynamic evolution of the overall coating microstructure. Laser-induced particle impact testing (LIPIT) has been extensively used to study single-particle impacts, and in this work is adapted to study the accumulation of numerous particles with knowledge of each individual particle's impact parameters (particle size, velocity). The method reproducibly deposits stacks of gold particles (>20 particles) with different characteristic spectra of impact velocity. The quantitative single-particle data are analyzed in a correlative manner to the structure and flaws in the resulting stacks, providing some first semi-quantitative connections between, e.g., strain and recrystallization, or aberrant particle characteristics and defects. The results highlight opportunities for the study of many-particle phenomena in microparticle impact--from interaction of particles in cold spray to multi-step erosion processes--with a quantitative view of the behavior of single particles.

Higher Landau-Level Analogues and Signatures of Non-Abelian States in Twisted Bilayer MoTe$_2$
Chong Wang, Xiao-Wei Zhang, Xiaoyu Liu, Jie Wang, Ting Cao, Di Xiao
arXiv:2404.05697v1 Announce Type: new Abstract: Recent experimental discovery of fractional Chern insulators at zero magnetic field in moir\'e superlattices has sparked intense interests in bringing Landau level physics to flat Chern bands. In twisted MoTe$_2$ bilayers (tMoTe$_2$), recent theoretical and experimental studies have found three consecutive flat Chern bands at twist angle $\sim 2^\circ$. In this work, we investigate whether higher Landau level physics can be found in these consecutive Chern bands. At twist angles $2.00^\circ$ and $1.89^\circ$, we identify four consecutive $C = 1$ bands for the $K$ valley in tMoTe$_2$. By constructing Wannier functions directly from density functional theory (DFT) calculations, a six-orbital model is developed to describe the consecutive Chern bands, with the orbitals forming a honeycomb lattice. Exact diagonalization on top of Hartree-Fock calculations are carried out with the Wannier functions. Especially, when the second moir\'e miniband is half-filled, signatures of non-Abelian states are found. Our Wannier-based approach in modelling moir\'e superlattices is faithful to DFT wave functions and can serve as benchmarks for continuum models. The possibility of realizing non-Abelian anyons at zero magnetic field also opens up a new pathway for fault-tolerant quantum information processing.

Infrared Spectroscopy for Diagnosing Superlattice Minibands in Magic-angle Twisted Bilayer Graphene
Geng Li, Roshan Krishna Kumar, Petr Stepanov, Pierre A. Pantale\'on, Zhen Zhan, Hitesh Agarwal, Adrien Bercher, Julien Barrier, Kenji Watanabe, Takashi Taniguchi, Alexey B. Kuzmenko, Francisco Guinea, Iacopo Torre, Frank H. L. Koppens
arXiv:2404.05716v1 Announce Type: new Abstract: Twisted bilayer graphene (TBG) represents a highly tunable, strongly correlated electron system owed to its unique flat electronic bands. However, understanding the single-particle band structure alone has been challenging due to complex lattice reconstruction effects and a lack of spectroscopic measurements over a broad energy range. Here, we probe the band structure of TBG around the magic angle using infrared spectroscopy. Our measurements reveal spectral features originating from interband transitions whose energies are uniquely defined by the twist angle. By combining with quantum transport, we connect spectral features over a broad energy range (10 to 700 meV) spanning several superlattice minibands and track their evolution with twist angle. We compare our data with calculations of the band structures obtained via the continuum model and find good agreement only when considering a variation of interlayer/intralayer tunnelling parameters with the twist angle. Our analysis suggests that the magic angle also shifts due to lattice relaxation, and is better defined for a wide angular range from 0.9{\deg} to 1.1{\deg}. Our work provides spectroscopic insights into TBG's band structure and offers an optical fingerprint of the magic angle for screening heterostructures before nanofabrication.

Comment on "Non-reciprocal topological solitons in active metamaterials"
Duilio De Santis, Bernardo Spagnolo, Angelo Carollo, Davide Valenti, Claudio Guarcello
arXiv:2404.04275v1 Announce Type: cross Abstract: In the recent work "Non-reciprocal topological solitons in active metamaterials" (see arXiv:2312.03544v1), for an analytical understanding of the system under consideration, the authors derive an ordinary differential equation for the sine-Gordon (anti)soliton velocity, with the perturbation theory in the adiabatic approximation, via the inverse scattering transform formalism, see Eq. (3) in their work. Here we note that the latter equation for the (anti)soliton velocity also follows from an energy balance approach.

Self-referencing photothermal common-path interferometry to measure absorption of Si3N4 membranes for laser-light sails
Demeng Feng, Tanuj Kumar, Shenwei Yin, Merlin Mah, Phyo Lin, Margaret Fortman, Gabriel R. Jaffe, Chenghao Wan, Hongyan Mei, Yuzhe Xiao, Ron Synowicki, Ronald J. Warzoha, Victor W. Brar, Joseph J. Talghader, Mikhail A. Kats
arXiv:2404.04449v1 Announce Type: cross Abstract: Laser-light sails are a spacecraft concept wherein lightweight "sails" are propelled to high speeds by lasers with high intensities. The sails must comprise materials with low optical loss, to minimize the risk of laser damage. Stoichiometric silicon nitride (Si$_3$N$_4$) is a candidate material with low loss in the near infrared, but the precise absorption coefficient has not been characterized in the membrane form-factor needed for sails. We use photothermal common-path interferometry (PCI), a sensitive pump-probe technique, to measure the absorption coefficient of stoichiometric and nonstoichiometric silicon nitride. To calibrate PCI measurements of membranes, we developed a self-referencing technique where a measurement is performed twice: once on a bare membrane, and a second time with a monolayer of graphene deposited on the membrane. The absorption of the sample with graphene can be measured by both PCI and more-conventional spectroscopic techniques, enabling the calibration of the PCI measurement. We find that with an absorption coefficient of (2.09 $\pm$ 0.76) $\times$ 10$^{-2}$ cm$^{-1}$ at 1064 nm, Si$_3$N$_4$ is a suitable laser-sail material for laser intensities as high as ~10 GW/m$^{2}$, which have been proposed for some laser-sail missions, while silicon-rich SiN$_x$ (x~1), with an absorption coefficient of 7.94 $\pm$ 0.50 cm$^{-1}$, is unlikely to survive such high laser intensities.

Incoherent non-Hermitian skin effect in photonic quantum walks
Stefano Longhi
arXiv:2404.04536v1 Announce Type: cross Abstract: The non-Hermitian skin effect describes the concentration of an extensive number of eigenstates near the boundaries of certain dissipative systems. This phenomenon has raised a huge interest in different areas of physics, including photonics, deeply expanding our understanding of non-Hermitian systems and opening up new avenues in both fundamental and applied aspects of topological phenomena. The skin effect has been associated to a nontrivial point-gap spectral topology and has been experimentally demonstrated in a variety of synthetic matter systems, including photonic lattices. In most of physical models exhibiting the non-Hermitian skin effect full or partial wave coherence is generally assumed. Here we push the concept of skin effect into the fully incoherent regime and show that rather generally (but not universally) the non-Hermitian skin effect persists under dephasing dynamics. The results are illustrated by considering incoherent light dynamics in non-Hermitian photonic quantum walks.

A Novel Class of Phase Space Representations for the Exact Population Dynamics of Two-State Quantum Systems and the Relation to Triangle Window Functions
Xiangsong Cheng, Xin He, Jian Liu
arXiv:2404.04868v1 Announce Type: cross Abstract: Isomorphism of the two-state system is heuristic in understanding the dynamical or statistical behavior of the simplest yet most quantum system that has no classical counterpart. We use constraint phase space [developed in J. Chem. Phys. 2016, 145, 204105; 2019, 151, 024105 and J. Phys. Chem. Lett. 2021, 12, 2496-2501], non-covariant phase space functions, time-dependent weight functions, and time-dependent normalization factors to construct a novel class of phase space representations of the exact population dynamics of the two-state quantum system. The equations of motion of the trajectory on constraint phase space are isomorphic to the time-dependent Schr\"odinger equation. The contribution of each trajectory to the integral expression for the population dynamics is always positive semi-definite. We also prove that the triangle window function approach, albeit empirically proposed in J. Chem. Phys. 2016, 145, 144108, is related to a special case of the novel class and leads to an isomorphic representation of the exact population dynamics of the two-state quantum system.

Comment on "Absence of Topological Protection of the Interface States in $\mathbb{Z}_2$ Photonic Crystals"
Xing-Xiang Wang, Toshikaze Kariyado, Xiao Hu
arXiv:2404.05156v1 Announce Type: cross Abstract: In the Letter, Xu et al. reported that edge modes disappear in the expanded structure of Wu-Hu model characterized by Z2 topological index, while appear in the trivial shrunken structure, when the edge cuts through the hexagonal unit cell. They then concluded that these edge modes are defect modes lacking topological protection. Unfortunately, their approach is not justified, rendering the conclusion unsolid.

Zincophilic armor: Phytate ammonium as a multifunctional additive for enhanced performance in aqueous zinc-ion batteries
Fangyuan Xiao, Xiaoke Wang, Kaitong Sun, Qian Zhao, Cuiping Han, Hai-Feng Li
arXiv:2404.05165v1 Announce Type: cross Abstract: Corrosion and the formation of by-products resulting from parasitic side reactions, as well as random dendrite growth, pose significant challenges for aqueous zinc-ion batteries (AZIBs). In this study, phytate ammonium is introduced into the traditional dilute Zinc sulfate electrolyte as a multi-functional additive. Leveraging the inherent zincophilic nature of the phytic anion, a protective layer is formed on the surface of the zinc anode. This layer can effectively manipulate the deposition process, mitigate parasitic reactions, and reduce the accumulation of detrimental by-products. Additionally, the competitive deposition between dissociated ammonium ions and Zn2+ promotes uniform deposition, thereby alleviating dendrite growth. Consequently, the modified electrolyte with a lower volume addition exhibits superior performance. The zinc symmetric battery demonstrates much more reversible plating/stripping, sustaining over 2000 hours at 5 mA cm-2 and 1 mA h cm-2. A high average deposition/stripping efficiency of 99.83% is achieved, indicating the significant boosting effect and practical potential of our strategy for high-performance aqueous zinc-ion batteries.

Experimental observation of a time rondeau crystal: Temporal Disorder in Spatiotemporal Order
Leo Joon Il Moon, Paul Manuel Schindler, Yizhe Sun, Emanuel Druga, Johannes Knolle, Roderich Moessner, Hongzheng Zhao, Marin Bukov, Ashok Ajoy
arXiv:2404.05620v1 Announce Type: cross Abstract: Our understanding of phases of matter relies on symmetry breaking, one example being water ice whose crystalline structure breaks the continuous translation symmetry of space. Recently, breaking of time translation symmetry was observed in systems not in thermal equilibrium. The associated notion of time crystallinity has led to a surge of interest, raising the question about the extent to which highly controllable quantum simulators can generate rich and tunable temporal orders, beyond the conventional classification of order in static systems. Here, we investigate different kinds of partial temporal orders, stabilized by non-periodic yet structured drives, which we call rondeau order. Using a $^{13}$C-nuclear-spin diamond quantum simulator, we report the first experimental observation of a -- tunable degree of -- short-time disorder in a system exhibiting long-time stroboscopic order. This is based on a novel spin control architecture that allows us to implement a family of drives ranging from structureless via structured random to quasiperiodic and periodic drives. Leveraging a high throughput read-out scheme, we continuously observe the spin polarization over 105 pulses to probe rondeau order, with controllable lifetimes exceeding 4 seconds. Using the freedom in the short-time temporal disorder of rondeau order, we show the capacity to encode information in the response of observables. Our work broadens the landscape of observed nonequilibrium temporal order, paving the way for new applications harnessing driven quantum matter.

Microscopic theory of nonlinear phase space filling in polaritonic lattices
Kok Wee Song, Salvatore Chiavazzo, Oleksandr Kyriienko
arXiv:2212.07968v3 Announce Type: replace Abstract: We develop a full microscopic theory for a nonlinear phase space filling (NPSF) in strongly coupled two-dimensional polaritonic lattices. Ubiquitous in polaritonic experiments, the theoretical description of NPSF, remains limited to perturbative treatment and homogeneous samples. In this study, we go beyond the existing theoretical description and discover the broad scope of regimes where NPSF crucially modifies the optical response. Studying the quantum effects of non-bosonicity, cooperative light-matter coupling, and Coulomb blockade, we reveal several regimes for observing the nonlinear Rabi splitting quench due to the phase space filling. Unlike prior studies, we derive nonlinear Rabi frequency scaling all the way to the saturation limit and show that the presence of a lattice potential leads to qualitatively distinct nonlinearity. We concentrate on three regimes of NPSF: 1) planar; 2) fractured; and 3) ultralocalized. In planar saturation, the Rabi frequency decreases exponentially as a function of exciton density. For the fractured case, where excitons form a lattice with sites exceeding the exciton size, we discover fast NPSF at low occupation in the lattice. This is followed by slower NPSF as the medium becomes fully saturated. This behavior is particularly pronounced in the presence of Coulomb (or Rydberg) blockade, where regions of fast and slow NPSF depend on the strength of repulsion. For the ultralocalized NPSF, we observe the square-root saturation typical to the collection of two-level systems. Our findings can help describing recent observations of strong nonlinearity in heterobilayers of transition metal dichalcogenides where Moir{\'e} lattices emerge naturally [Nature \textbf{591}, 61 (2021)]. The theory also opens the prospects for engineering strongly nonlinear responses of polaritonic lattices with patterned samples, driving polaritonics into the quantum regime.

Understanding and Optimizing the Sensitization of Anatase Titanium Dioxide Surface with Hematite Clusters
Kati Asikainen, Matti Alatalo, Marko Huttula, Bernardo Barbiellini, S. Assa Aravindh
arXiv:2301.11034v3 Announce Type: replace Abstract: The presence of small hematite (Fe2O3) clusters at low coverage on titanium dioxide (TiO2) surface has been observed to enhance photocatalytic activity, while excess loading of hematite is detrimental. We conduct a comprehensive density functional theory study of Fe2O3 clusters adsorbed on the anatase TiO2 (101) surface to investigate the effect of Fe2O3 on TiO2. Our study shows that TiO2 exhibits improved photocatalytic properties with hematite clusters at low coverage, as evidenced by a systematic study conducted by increasing the number of cluster adsorbates. The adsorption of the clusters generates impurity states in the band gap improving light absorption and consequently affecting the charge transfer dynamics. Furthermore, the presence of hematite clusters enhances the activity of TiO2 in the hydrogen evolution reaction. The Fe valence mixing present in some clusters leads to a significant increase in H2 evolution rate compared with the fixed +3 valence of Fe in hematite. We also investigate the effect of oxygen defects and find extensive modifications in the electronic properties and local magnetism of the TiO2 - Fe2O3 system, demonstrating the wide-ranging effect of oxygen defects in the combined system.

Superconducting Diode Effect Sign Change in Epitaxial Al-InAs Josepshon Junctions
Neda Lotfizadeh, William F. Schiela, Bar{\i}\c{s} Pekerten, Peng Yu, Bassel Heiba Elfeky, William Strickland, Alex Matos-Abiague, Javad Shabani
arXiv:2303.01902v3 Announce Type: replace Abstract: There has recently been a surge of interest in studying the superconducting diode effect (SDE) partly due to the possibility of uncovering the intrinsic properties of a material system. A change of sign of the SDE at finite magnetic field has previously been attributed to different mechanisms. Here, we observe the SDE in epitaxial Al-InAs Josephson junctions with strong Rashba spin-orbit coupling (SOC). We show that this effect strongly depends on the orientation of the in-plane magnetic field. In the presence of a strong magnetic field, we observe a change of sign in the SDE. Simulation and measurement of supercurrent suggest that depending on the superconducting widths, $W_\text{S}$, this sign change may not necessarily be related to 0--$\pi$ or topological transitions. We find that the strongest sign change in junctions with narrow $W_\text{S}$ is consistent with SOC-induced asymmetry of the critical current under magnetic-field inversion, while in wider $W_\text{S}$, the sign reversal could be related to 0--$\pi$ transitions and topological superconductivity.

Emus live on the Gross-Neveu-Yukawa archipelago
Ting-Tung Wang, Zi Yang Meng
arXiv:2304.00034v3 Announce Type: replace Abstract: It is expected that the Gross-Neveu-Yukawa (GNY) chiral Ising transition of $N$ Majorana (or $N_f=N/4$ four-component Dirac) fermions coupled with scalar field in (2+1)D will be the first fermionic quantum critical point that various methods such as conformal bootstrap [1], perturbative renormalization group [2] and quantum Monte Carlo (QMC) simulations [3], would yield the converged critical exponents -- serving the same textbook role as the Ising and $O(N)$ models in the statistical and quantum phase transition. However, such expectation has not been fully realized from the lattice QMC simulations due to the obstacles introduced by the UV finite size effect. In this work, by means of the elective-momentum ultra-size (EMUS) QMC method [4], we compute the critical exponents of the GNY $N=8$ chiral Ising transition on a 2D $\pi$-flux fermion lattice model between Dirac semimetal and quantum spin Hall insulator phases [3, 5]. With the matching of fermionic and bosonic momentum transfer and collective update in momentum space, our QMC results provide the fully consistent exponents with those obtained from the bootstrap and perturbative approaches. In this way, the Emus now live happily on the $N=8$ island and could explore the Gross-Neveu-Yukawa archipelago [1] with ease.

CVD Graphene Contacts for Lateral Heterostructure MoS${_2}$ Field Effect Transistors
Daniel S. Schneider, Leonardo Lucchesi, Eros Reato, Zhenyu Wang, Agata Piacentini, Jens Bolten, Damiano Marian, Enrique G. Marin, Aleksandra Radenovic, Zhenxing Wang, Gianluca Fiori, Andras Kis, Giuseppe Iannaccone, Daniel Neumaier, Max C. Lemme
arXiv:2304.01177v2 Announce Type: replace Abstract: Intensive research is carried out on two-dimensional materials, in particular molybdenum disulfide, towards high-performance transistors for integrated circuits. Fabricating transistors with ohmic contacts is challenging due to the high Schottky barrier that severely limits the transistors' performance. Graphene-based heterostructures can be used in addition or as a substitute for unsuitable metals. We present lateral heterostructure transistors made of scalable chemical vapor-deposited molybdenum disulfide and chemical vapor-deposited graphene with low contact resistances of about 9 k${\Omega}$${\mu}$m and high on/off current ratios of 10${^8}$. We also present a theoretical model calibrated on our experiments showing further potential for scaling transistors and contact areas into the few nanometers range and the possibility of a strong performance enhancement by means of layer optimizations that would make transistors promising for use in future logic circuits.

Abundant surface-semimetal phases in three-dimensional obstructed atomic insulators
Xianyong Ding, Xin Jin, Zhuo Chen, Xuewei Lv, Da-Shuai Ma, Xiaozhi Wu, Rui Wang
arXiv:2304.01713v2 Announce Type: replace Abstract: Three-dimensional obstructed atomic insulators (OAIs) are characterized by the appearance of floating surface states (FSSs) at specific surfaces. Benefiting from this feature, our study here shows the presence of abundant surface-semimetal phases in 3D OAIs. The symmetries of obstructed Wannier charge centers ensure the degeneracy of such FSSs at high-symmetry points or invariant lines in the surface Brillouin zone. Utilizing topological quantum chemistry theory, we identify a carbon allotrope with a body-centered tetragonal structure, named bct-C20, as an ideal candidate for realizing different kinds of surface-semimetal phases. For the (001)surface of bct-C20, there are four in-gap FSSs, and these four FSSs form two kinds of surface Dirac cones, i.e., topological Dirac cones with linear dispersion and symmetry-enforced quadratic Dirac cones. The band topology of a surface Dirac cone is captured by the effective surface Hamiltonian and the emergence of hinge states. Moreover, the existence of the surface-nodal-line state is also discussed. This work reports an approach to obtain d-dimensional semimetal phases from the surface states of (d + 1)-dimensional systems, which is of great significance for the studies in revealing topological states and their practical applications in high-dimensional crystals.

Fermionic skyrmions and bosonization for a Gross-Neveu transition
Xiao Yan Xu, Tarun Grover
arXiv:2304.13716v2 Announce Type: replace Abstract: We investigate a 2+1-D interacting Dirac semimetal with onsite flavor SU(2) symmetry. Topological considerations imply that the skyrmions in the flavor-symmetry-breaking phase carry electron quantum numbers, motivating a dual bosonized low energy description in terms of two complex scalars coupled to an abelian Chern-Simons field. We propose that the transition between a nearby Chern insulator and the flavor symmetry-broken phase is a bicritical point in the bosonized description, and also suggest that the Gross-Neveu-Heisenberg (GNH) transition between the Dirac semimetal and the flavor symmetry-broken phase is a tricritical point. Heuristically, the dual description corresponds to the gap closing of fermionic skyrmions. We discuss implications and potential issues with our proposal, and motivated from it, perform extensive unbiased Determinantal Quantum Monte Carlo (DQMC) simulations on a lattice regularized Hamiltonian for the GNH transition, extending previously available results. We compare DQMC results with the estimates in the proposed dual from available perturbative renormalization group results. We also numerically demonstrate the presence of fermionic skyrmions in the symmetry-broken phase of our lattice model.

Magnetic field induced partially polarized chiral spin liquid in a transition metal dichalcogenide moir\'e system
Yixuan Huang, D. N. Sheng, Jian-Xin Zhu
arXiv:2306.03056v2 Announce Type: replace Abstract: As one of the most intriguing states of matter, the chiral spin liquid (CSL) has attracted much scientific interest while its existence and mechanism in crystalline strongly correlated systems remain hotly debated. On the other hand, strong correlation driven emergent phenomena can be realized in twisted transition metal dichalcogenide bilayers with a tremendously tunable large length scale providing a new platform for the emergence of CSLs. We focus on a strongly correlated model relevant to heterobilayer $\textrm{WSe}_{2}/\textrm{MoSe}_{2}$ and investigate the Mott insulating phase at half filling under an out-of-plane magnetic field. Considering both its orbital and spin Zeeman effects we identify three conventionally ordered phases including a $120^{\circ}$ N\'{e}el phase, a stripe phase, and an up-up-down phase. For intermediate fields an emergent quantum spin liquid phase is identified with partial spin polarization. We further characterize its topological nature as the $\nu$ = 1/2 Laughlin CSL through the topological entanglement spectrum and quantized spin pumping under spin flux insertion. In addition, we map out the quantum phase diagram for different twisted angles in an experimentally accessible parameter regime.

Chirality probe of twisted bilayer graphene in the linear transport regime
Dario A. Bahamon, Guillermo G\'omez-Santos, Dmitri K. Efetov, Tobias Stauber
arXiv:2307.03779v2 Announce Type: replace Abstract: We propose minimal transport experiments in the coherent regime that can probe the chirality of twisted moir\'e structures. We show that only with a third contact and in the presence of an in-plane magnetic field (or other time-reversal symmetry breaking effect), a chiral system may display non-reciprocal transport in the linear regime. We then propose to use the third lead as a voltage probe and show that opposite enantiomers give rise to different voltage drops on the third lead. Additionally, in the scenario of layer-discriminating contacts, the third lead can serve as a current probe, capable of detecting different handedness even in the absence of a magnetic field. In a complementary configuration, applying opposite voltages on the two layers of the third leads gives rise to a chiral (super)current in the absence of a source-drain voltage whose direction is determined by its chirality.

Nonlinear optical diode effect in a magnetic Weyl semimetal
Christian Tzschaschel, Jian-Xiang Qiu, Xue-Jian Gao, Hou-Chen Li, Chunyu Guo, Hung-Yu Yang, Cheng-Ping Zhang, Ying-Ming Xie, Yu-Fei Liu, Anyuan Gao, Damien B\'erub\'e, Thao Dinh, Sheng-Chin Ho, Yuqiang Fang, Fuqiang Huang, Johanna Nordlander, Qiong Ma, Fazel Tafti, Philip J. W. Moll, Kam Tuen Law, Su-Yang Xu
arXiv:2307.15603v2 Announce Type: replace Abstract: Diode effects are of great interest for both fundamental physics and modern technologies. Electrical diode effects (nonreciprocal transport) have been observed in Weyl systems. Optical diode effects arising from the Weyl fermions have been theoretically considered but not probed experimentally. Here, we report the observation of a nonlinear optical diode effect (NODE) in the magnetic Weyl semimetal CeAlSi, where the magnetization introduces a pronounced directionality in the nonlinear optical second-harmonic generation (SHG). We show demonstrate a six-fold change of the measured SHG intensity between opposite propagation directions over a bandwidth exceeding 250 meV. Supported by density-functional theory, we establish the linearly dispersive bands emerging from Weyl nodes as the origin of this broadband effect. We further demonstrate current-induced magnetization switching and thus electrical control of the NODE. Our results advance ongoing research to identify novel nonlinear optical/transport phenomena in magnetic topological materials and further opens new pathways for the unidirectional manipulation of light.

Discovery of smectic charge and pair-density-wave orders in topological monolayer 1T$^\prime$-MoTe$_2$
Li-Xuan Wei, Peng-Cheng Xiao, Fangsen Li, Li Wang, Bo-Yuan Deng, Fang-Jun Cheng, Fa-Wei Zheng, Ning Hao, Ping Zhang, Xu-Cun Ma, Qi-Kun Xue, Can-Li Song
arXiv:2308.11101v2 Announce Type: replace Abstract: Electronic liquid-crystal phases are observed in numerous strongly-correlated systems including high-temperature superconductors. However, identifying these exotic phases and understanding their interplay with superconductivity in topological materials remain challenging. Here we employ a cryogenic scanning tunneling microscopy to discover a smectic (stripe) charge order (CO) and a primary pair-density-wave (PDW) in topological monolayer 1T$^\prime$-MoTe$_2$. The two orders are spatially modulated unidirectionally at the same wavevector, but have a marked spatial phase difference of about 2$\pi$/5. Importantly, the primary PDW state features a two-gap superconductivity below the transition temperature of 6.0 K and induces another unique particle-hole-symmetric CO at twice the PDW wavevector. Combining these results and our density functional calculations, we reveal that the two smectic orders are primarily driven by nesting behaviors between electron and hole pockets. Our findings establish monolayer 1T$^\prime$-MoTe$_2$ as a topological paradigm for exploring electronic smecticity, which intertwines with multiple preexisting symmetry-breaking states.

Higher-group symmetry of (3+1)D fermionic $\mathbb{Z}_2$ gauge theory: logical CCZ, CS, and T gates from higher symmetry
Maissam Barkeshli, Po-Shen Hsin, Ryohei Kobayashi
arXiv:2311.05674v3 Announce Type: replace Abstract: It has recently been understood that the complete global symmetry of finite group topological gauge theories contains the structure of a higher-group. Here we study the higher-group structure in (3+1)D $\mathbb{Z}_2$ gauge theory with an emergent fermion, and point out that pumping chiral $p+ip$ topological states gives rise to a $\mathbb{Z}_{8}$ 0-form symmetry with mixed gravitational anomaly. This ordinary symmetry mixes with the other higher symmetries to form a 3-group structure, which we examine in detail. We then show that in the context of stabilizer quantum codes, one can obtain logical CCZ and CS gates by placing the code on a discretization of $T^3$ (3-torus) and $T^2 \rtimes_{C_2} S^1$ (2-torus bundle over the circle) respectively, and pumping $p+ip$ states. Our considerations also imply the possibility of a logical $T$ gate by placing the code on $\mathbb{RP}^3$ and pumping a $p+ip$ topological state.

Symmetry, topology, duality, chirality, and criticality in a spin-1/2 XXZ ladder with a four-spin interaction
Mateo Fontaine, Koudai Sugimoto, Shunsuke Furukawa
arXiv:2311.07053v3 Announce Type: replace Abstract: We study the ground-state phase diagram of a spin-1/2 XXZ model with a chirality-chirality interaction (CCI) on a two-leg ladder. This model offers a minimal setup to study an interplay between spin and chirality degrees of freedom. The spin-chirality duality transformation allows us to relate the regimes of weak and strong CCIs. By applying the Abelian bosonization and the duality, we obtain a rich phase diagram that contains distinct gapped featureless and ordered phases. In particular, Neel and vector chiral orders appear for easy-axis anisotropy, while two distinct symmetry protected topological (SPT) phases appear for easy-plane anisotropy. The two SPT phases can be viewed as twisted variants of the Haldane phase. We also present an effective description in terms of (spinor) hard-core bosons, which reveals critical behavior on the self-dual line in the easy-axis and easy-plane regimes. We perform numerical simulations to confirm the predicted phase structure and critical properties. We further demonstrate that the two SPT phases and a trivial phase are distinguished by topological indices in the presence of certain symmetries. A similar phase structure is expected in a spin-1/2 XXZ ladder with four-spin ring exchange.

Electrical control and transport of tightly bound interlayer excitons in a MoSe2/hBN/MoSe2 heterostructure
Lifu Zhang, Ruihao Ni, Liuxin Gu, Ming Xie, Suji Park, Houk Jang, Takashi Taniguchi, Kenji Watanabe, You Zhou
arXiv:2312.02446v2 Announce Type: replace Abstract: Controlling interlayer excitons in van der Waals heterostructures holds promise for exploring Bose-Einstein condensates and developing novel optoelectronic applications, such as excitonic integrated circuits. Despite intensive studies, several key fundamental properties of interlayer excitons, such as their binding energies and interactions with charges, remain not well understood. Here we report the formation of momentum-direct interlayer excitons in a high-quality MoSe2/hBN/MoSe2 heterostructure under an electric field, characterized by bright photoluminescence (PL) emission with high quantum yield and a narrow linewidth of less than 4 meV. These interlayer excitons show electrically tunable emission energy spanning ~180 meV through the Stark effect, and exhibit a sizable binding energy of ~81 meV in the intrinsic regime, along with trion binding energies of a few millielectronvolts. Remarkably, we demonstrate the long-range transport of interlayer excitons with a characteristic diffusion length exceeding ten micrometers, which can be attributed, in part, to their dipolar repulsive interactions. Spatially and polarization-resolved spectroscopic studies reveal rich exciton physics in the system, such as valley polarization, local trapping, and the possible existence of dark interlayer excitons. The formation and transport of tightly bound interlayer excitons with narrow linewidth, coupled with the ability to electrically manipulate their properties, open exciting new avenues for exploring quantum many-body physics, including excitonic condensate and superfluidity, and for developing novel optoelectronic devices, such as exciton and photon routers.

Gauge symmetry of excited states in projected entangled-pair state simulations
Yi Tan, Ji-Yao Chen, Didier Poilblanc, Jia-Wei Mei
arXiv:2312.04555v2 Announce Type: replace Abstract: While gauge symmetry is a well-established requirement for representing topological orders in projected entangled-pair state (PEPS), its impact on the properties of low-lying excited states remains relatively unexplored. Here we perform PEPS simulations of low-energy dynamics in the Kitaev honeycomb model, which supports fractionalized gauge flux (vison) excitations. We identify gauge symmetry emerging upon optimizing an unbiased PEPS ground state. Using the PEPS adapted local mode approximation, we further classify the low-lying excited states by discerning different vison sectors. Our simulations of spin and spin-dimer dynamical correlations establish close connections with experimental observations. Notably, the selection rule imposed by the locally conserved visons results in nearly flat dispersions in momentum space for excited states belonging to the 2-vison or 4-vison sectors.

Bendability parameter for twisted ribbons to describe longitudinal wrinkling and delineate the near-threshold regime
Madelyn Leembruggen, Jovana Andrejevic, Arshad Kudrolli, Chris H. Rycroft
arXiv:2401.10797v3 Announce Type: replace Abstract: We propose a dimensionless bendability parameter, $\epsilon^{-1} = [\left(h/W\right)^2 T^{-1}]^{-1}$ for wrinkling of thin, twisted ribbons with thickness $h$, width $W$, and tensional strain $T$. Bendability permits efficient collapse of data for wrinkle onset, wavelength, critical stress, and residual stress, demonstrating longitudinal wrinkling's primary dependence on this parameter. This new parameter also allows us to distinguish the highly bendable range ($\epsilon^{-1} > 20$) from moderately bendable samples ($\epsilon^{-1} \in (0,20]$). We identify scaling relations to describe longitudinal wrinkles that are valid across our entire set of simulated ribbons. When restricted to the highly bendable regime, simulations confirm theoretical near-threshold (NT) predictions for wrinkle onset and wavelength.

The Influence of Chemical Strains on the Electrocaloric Response, Polarization Morphology, Tetragonality and Negative Capacitance Effect of Ferroelectric Core-Shell Nanorods and Nanowires
Anna N. Morozovska, Eugene A. Eliseev, Olha A. Kovalenko, Dean R. Evans
arXiv:2402.06797v3 Announce Type: replace Abstract: Using Landau-Ginzburg-Devonshire (LGD) approach we proposed the analytical description of the chemical strains influence on the spontaneous polarization and electrocaloric response in ferroelectric core-shell nanorods. We postulate that the nanorod core presents a defect-free single-crystalline ferroelectric material, and the elastic defects are accumulated in the ultra-thin shell, where they can induce tensile or compressive chemical strains. The finite element modeling (FEM) based on the LGD approach reveals transitions of domain structure morphology induced by the chemical strains in the BaTiO3 nanorods. Namely, tensile chemical strains induce and support the single-domain state in the central part of the nanorod, while the curled domain structures appear near the unscreened or partially screened ends of the rod. The vortex-like domains propagate toward the central part of the rod and fill it entirely, when the rod is covered by a shell with compressive chemical strains above some critical value. The critical value depends on the nanorod sizes, aspect ratio, and screening conditions at its ends. Both analytical theory and FEM predict that the tensile chemical strains in the shell increase the nanorod polarization, lattice tetragonality, and electrocaloric response well-above the values corresponding to the bulk material. The physical reason of the increase is the strong electrostriction coupling between the mismatch-type elastic strains induced in the core by the chemical strains in the shell. Comparison with the earlier XRD data confirmed an increase of tetragonality ratio in tensiled BaTiO3 nanorods compared to the bulk material.

Repulsive Casimir force from a Majorana zero-mode
C. W. J. Beenakker
arXiv:2402.13862v3 Announce Type: replace Abstract: Fu and Kane have taught us that a Majorana zero-mode appears on the quantum spin Hall edge at the interface with a superconductor. If a magnetic scatterer is placed on the edge, the zero-point energy of massless edge excitations exerts a force on the scatterer. This is the fermionic analogue of the electromagnetic Casimir effect. We show that the Majorana zero-mode produces a repulsive Casimir force, pushing the scatterer away from the superconductor. Unlike some other signatures of Majorana zero-modes, the repulsive Casimir force is directly tied to the topological invariant of the system (the sign of the determinant of the reflection matrix from the superconductor).

Nematic versus Kekul\'e phases in twisted bilayer graphene under hydrostatic pressure
Miguel S\'anchez S\'anchez, Israel D\'iaz, Jos\'e Gonz\'alez, Tobias Stauber
arXiv:2403.03140v2 Announce Type: replace Abstract: We address the precise determination of the phase diagram of magic angle twisted bilayer graphene under hydrostatic pressure within a self-consistent Hartree-Fock method in real space, including all the remote bands of the system. We further present a novel algorithm that maps the full real-space density matrix to a reduced density matrix based on a $SU(4)$ symmetry of sublattice and valley degrees of freedom. We find a quantum critical point between a nematic and a Kekul\'e phase, and show also that our microscopic approach displays a strong particle-hole asymmetry in the weak coupling regime. We arrive then at the prediction that the superconductivity should be Ising-like in the hole-doped nematic regime, with spin-valley locking, and spin-triplet in the electron-doped regime.

Exciton-activated effective phonon magnetic moment in monolayer MoS2
Chunli Tang, Gaihua Ye, Cynthia Nnokwe, Mengqi Fang, Li Xiang, Masoud Mahjouri-Samani, Dmitry Smirnov, Eui-Hyeok Yang, Tingting Wang, Lifa Zhang, Rui He, Wencan Jin
arXiv:2403.15347v2 Announce Type: replace Abstract: Optical excitation of chiral phonons plays a vital role in studying the phonon-driven magnetic phenomena in solids. Transition metal dichalcogenides host chiral phonons at high symmetry points of the Brillouin zone, providing an ideal platform to explore the interplay between chiral phonons and valley degree of freedom. Here, we investigate the helicity-resolved magneto-Raman response of monolayer MoS2 and identify a doubly degenerate Brillouin-zone-center chiral phonon mode at ~270 cm-1. Our wavelength- and temperature-dependent measurements show that this chiral phonon is activated through the resonant excitation of A exciton. Under an out-of-plane magnetic field, the chiral phonon exhibits giant Zeeman splitting, which corresponds to an effective magnetic moment of ~2.5mu_B. Moreover, we carry out theoretical calculations based on the morphic effects in nonmagnetic crystals, which reproduce the linear Zeeman splitting and Raman cross-section of the chiral phonon. Our study provides important insights into lifting the chiral phonon degeneracy in an achiral covalent material, paving a new route to excite and control chiral phonons.

Retaining Landau quasiparticles in the presence of realistic charge fluctuations in cuprates
Hiroyuki Yamase, Matias Bejas, Andres Greco
arXiv:2404.02200v2 Announce Type: replace Abstract: Charge excitation spectra are getting clear in cuprate superconductors in momentum-energy space especially around a small momentum region, where plasmon excitations become dominant. Here, we study whether Landau quasiparticles survive in the presence of charge fluctuations observed in experiments. We employ the layered t-J model with the long-range Coulomb interaction, which can reproduce the realistic charge fluctuations. We find that Landau quasiparticles are retained in a realistic temperature and doping region, although the quasiparticle spectral weight is strongly reduced to 0.08-0.24. Counterintuitively, the presence of this small quasiparticle weight does not work favorably to generate a pseudogap.

The geometry of high-dimensional phase diagrams: I. Generalized Gibbs Phase Rule
Wenhao Sun, Matthew J. Powell-Palm, Jiadong Chen
arXiv:2105.01337v2 Announce Type: replace-cross Abstract: Significance Statement Phase diagrams are essential tools of the materials scientist, showing which phases are at equilibrium under a set of applied thermodynamic conditions. Essentially all phase diagrams today are two dimensional, typically constructed with axes of temperature-pressure or temperature-composition. For many modern materials, it would be valuable to construct phase diagrams that include additional forms of thermodynamic work--such as elastic, surface, electromagnetic or electrochemical work, etc.--which grows the free energy of materials into higher (>3) dimensions. Here, we extend Gibbs' original arguments on phase coexistence to derive a generalized Phase Rule, based in the combinatorial geometry of high-dimensional convex polytopes. The generalized Phase Rule offers a conceptual and geometric foundation to describe phase boundaries on high-dimensional phase diagrams, which are relevant for understanding the stability of modern materials in complex chemical environments. Abstract We revisit Gibbs arguments on the equilibrium of heterogeneous substances and show that phase coexistence regions in high-dimensional Internal Energy space, U(S,Xi,...,Xj), are simplicial convex polytopes--which are N-dimensional analogues of triangles and tetrahedra. In the first of this three-part series, we examine how the combinatorial relationships between the vertices and facets of simplicial polytopes leads to a generalized high-dimensional description of Gibbs' Phase Rule. Because Gibbs' Phase Rule describes the nature of phase boundaries on phase diagrams, this isomorphism between the physical principles of equilibrium thermodynamics and the geometry of simplicial polytopes provides the foundation to construct generalized phase diagrams, which can exist in any dimension, with any intensive or extensive thermodynamic variable on the axes.

Learnability transitions in monitored quantum dynamics via eavesdropper's classical shadows
Matteo Ippoliti, Vedika Khemani
arXiv:2307.15011v3 Announce Type: replace-cross Abstract: Monitored quantum dynamics -- unitary evolution interspersed with measurements -- has recently emerged as a rich domain for phase structure in quantum many-body systems away from equilibrium. Here we study monitored dynamics from the point of view of an eavesdropper who has access to the classical measurement outcomes, but not to the quantum many-body system. We show that a measure of information flow from the quantum system to the classical measurement record -- the informational power -- undergoes a phase transition in correspondence with the measurement-induced phase transition (MIPT). This transition determines the eavesdropper's (in)ability to learn properties of an unknown initial quantum state of the system, given a complete classical description of the monitored dynamics and arbitrary classical computational resources. We make this learnability transition concrete by defining classical shadows protocols that the eavesdropper may apply to this problem, and show that the MIPT manifests as a transition in the sample complexity of various shadow estimation tasks, which become harder in the low-measurement phase. We focus on three applications of interest: Pauli expectation values (where we find the MIPT appears as a point of optimal learnability for typical Pauli operators), many-body fidelity, and global charge in $U(1)$-symmetric dynamics. Our work unifies different manifestations of the MIPT under the umbrella of learnability and gives this notion a general operational meaning via classical shadows.

Analytical Modeling of Acoustic Exponential Materials and Physical Mechanism of Broadband Anti-Reflection
Sichao Qu, Min Yang, Tenglong Wu, Yunfei Xu, Nicholas Fang, Shuyu Chen
arXiv:2309.03538v3 Announce Type: replace-cross Abstract: Spatially exponential distributions of material properties are ubiquitous in many natural and engineered systems, from the vertical distribution of the atmosphere to acoustic horns and anti-reflective coatings. These media seamlessly interface different impedances, enhancing wave transmission and reducing internal reflections. This work advances traditional transfer matrix theory by integrating analytical solutions for acoustic exponential materials, which possess exponential density and/or bulk modulus, offering a more accurate predictive tool and revealing the physical mechanism of broadband anti-reflection for sound propagation in such non-uniform materials. Leveraging this method, we designed an acoustic dipole array that effectively mimics exponential mass distribution. Through experiments with precisely engineered micro-perforated plates, we demonstrate an ultra-low reflection rate of about 0.86% across a wide frequency range from 420 Hz to 10,000 Hz. Our modified transfer matrix approach underpins the design of exponential materials, and our layering strategy for stacking acoustic dipoles suggests a pathway to more functional gradient acoustic metamaterials.

Accurate Hyperfine Tensors for Solid State Quantum Applications: Case of the NV Center in Diamond
Istv\'an Tak\'acs, Viktor Iv\'ady
arXiv:2309.03983v2 Announce Type: replace-cross Abstract: The decoherence of point defect qubits is often governed by the electron spin-nuclear spin hyperfine interaction that can be parameterized by using ab inito calculations in principle. So far most of the theoretical works have focused on the hyperfine interaction of the closest nuclear spins, while the accuracy of the predictions for distinct nuclear spins is barely discussed. We demonstrate for the case of the NV center in diamond that the absolute relative error of the computed hyperfine parameters can exceed 100\% in VASP for weakly coupled nuclear spins. To overcome this issue, we implement an alternative method and report on significantly improved hyperfine values with $O$(1\%) relative mean error at all distances. The provided accurate hyperfine data for the NV center enables high-precision simulation of NV quantum nodes for quantum information processing and positioning of nuclear spins by comparing experimental and theoretical hyperfine data.

Found 9 papers in prb
Date of feed: Tue, 09 Apr 2024 03:17:08 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)

Catching thermal avalanches in the disordered XXZ model
Tomasz Szołdra, Piotr Sierant, Maciej Lewenstein, and Jakub Zakrzewski
Author(s): Tomasz Szołdra, Piotr Sierant, Maciej Lewenstein, and Jakub Zakrzewski

Strong disorder in many-body quantum systems leads to many-body localization (MBL), manifested as long-time memory of the initial state. Spatial regions of anomalously weak disorder, arising due to fluctuations in the disordered potential, may act as ergodic inclusions that seed quantum avalanches and destabilize the MBL. To investigate this mechanism in a controlled setting, the authors plant ergodic inclusions by engineering regions of a weak disorder and compare the system’s time evolution with predictions of the avalanche theory.

[Phys. Rev. B 109, 134202] Published Mon Apr 08, 2024

Type-II superconductivity in the Dirac semimetal ${\mathrm{PdTe}}_{2}$
Ritu Gupta, Catherine Witteveen, Debarchan Das, Fabian O. von Rohr, and Rustem Khasanov
Author(s): Ritu Gupta, Catherine Witteveen, Debarchan Das, Fabian O. von Rohr, and Rustem Khasanov

We report on the microscopic superconducting properties of the Dirac semimetal ${\mathrm{PdTe}}_{2}$. In this study, we have focused on mosaic crystals of ${\mathrm{PdTe}}_{2}$, and used detailed zero-field and transverse-field muon-spin relaxation/rotation $(μ\mathrm{SR})$, ac-magnetic susceptibili…

[Phys. Rev. B 109, 134507] Published Mon Apr 08, 2024

Sound velocity of α-quartz under pressure: First-principles calculations
Zhi-Xin Bai, Xin Qu, Cheng-Lu Jiang, Zheng-Tang Liu, and Qi-Jun Liu
Author(s): Zhi-Xin Bai, Xin Qu, Cheng-Lu Jiang, Zheng-Tang Liu, and Qi-Jun Liu

As the most abundant substance on the earth's crust, the behavior of α-quartz under pressure has always been a research hotspot, which has inherent crystallographic significance and is of significance to understanding the rocky parts of the earth. This paper provides the discussion about the stabili…

[Phys. Rev. B 109, 144105] Published Mon Apr 08, 2024

Realizing attractive interacting topological surface fermions: A resonating topological-insulator–thin-film hybrid platform
Saran Vijayan and Fei Zhou
Author(s): Saran Vijayan and Fei Zhou

In this paper, we propose a practical way to realize topological surface Dirac fermions with tunable attractive interaction between them. The approach involves coating the surface of a topological insulator with a thin-film metal and utilizing the strong-electron phonon coupling in the metal to indu…

[Phys. Rev. B 109, 144508] Published Mon Apr 08, 2024

Engineering the in-plane anomalous Hall effect in ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ thin films
Wangqian Miao, Binghao Guo, Susanne Stemmer, and Xi Dai
Author(s): Wangqian Miao, Binghao Guo, Susanne Stemmer, and Xi Dai

We predict two topological phase transitions for cadmium arsenide $({\mathrm{Cd}}_{3}{\mathrm{As}}_{2})$ thin films under in-plane magnetic field, taking advantage of a four-band $k·p$ model and effective $g$ factors calculated from first principles. Film thickness, growth direction, and in-plane Ze…

[Phys. Rev. B 109, 155408] Published Mon Apr 08, 2024

Topological origin of antichiral edge states induced by a nonchiral phonon
Yunlong Su and Gang Li
Author(s): Yunlong Su and Gang Li

In contrast to the chiral edge modes, the antichiral edge modes propagate in the same direction along two parallel boundaries, representing a new state that provides more possibility for the dissipationless transportation of information. In a recent work by Medina Dueñas et al. [Phys. Rev. Lett. 128

[Phys. Rev. B 109, 155410] Published Mon Apr 08, 2024

Topological properties of nearly flat bands in bilayer $α−{T}_{3}$ lattice
Puspita Parui, Sovan Ghosh, and Bheema Lingam Chittari
Author(s): Puspita Parui, Sovan Ghosh, and Bheema Lingam Chittari

We study the effect of Haldane flux in the bilayer $α\text{−}{\mathcal{T}}_{3}$ lattice system, considering possible nonequivalent, commensurate stacking configurations with a tight-binding formalism. The bilayer $α\text{−}{\mathcal{T}}_{3}$ lattice comprises six sublattices in a unit cell, and its …

[Phys. Rev. B 109, 165118] Published Mon Apr 08, 2024

Topological band structure due to modified Kramers degeneracy for electrons in a helical magnetic field
Yu. B. Kudasov
Author(s): Yu. B. Kudasov

Two theorems on electron states in helimagnets are proved. They reveal a Kramers-like degeneracy in a helical magnetic field. Since a commensurate helical magnetic system is transitionally invariant with two multiple periods (ordinary translations and generalized ones with rotations), the band struc…

[Phys. Rev. B 109, L140402] Published Mon Apr 08, 2024

Proximity-effect-induced superconductivity in a van der Waals heterostructure consisting of a magnetic topological insulator and a conventional superconductor
Peng Dong, Xiaofei Hou, Jiadian He, Yiwen Zhang, Yifan Ding, Xiaohui Zeng, Jinghui Wang, Yueshen Wu, Kenji Watanabe, Takashi Taniguchi, Wei Xia, Yanfeng Guo, Yulin Chen, Xiang Zhou, Wei Li, and Jun Li
Author(s): Peng Dong, Xiaofei Hou, Jiadian He, Yiwen Zhang, Yifan Ding, Xiaohui Zeng, Jinghui Wang, Yueshen Wu, Kenji Watanabe, Takashi Taniguchi, Wei Xia, Yanfeng Guo, Yulin Chen, Xiang Zhou, Wei Li, and Jun Li

Nontrivial topological superconductivity has received enormous attention due to its potential applications in topological quantum computing. The intrinsic issue concerning the correlation between a topological insulator and a superconductor is, however, still widely open. Here, we systemically repor…

[Phys. Rev. B 109, L140503] Published Mon Apr 08, 2024

Found 7 papers in nano-lett
Date of feed: Mon, 08 Apr 2024 13:16:40 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] Chirality Probe of Twisted Bilayer Graphene in the Linear Transport Regime
Dario A. Bahamon, Guillermo Gómez-Santos, Dmitri K. Efetov, and Tobias Stauber

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00371

[ASAP] Electrical Transport and Dynamics of Confined DNA through Highly Conductive 2D Graphene Nanochannels
Yangjun Cui, Cuifeng Ying, Xiao-Yu Huang, Qing Ye, Jianguo Tian, and Zhibo Liu

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00403

[ASAP] Photonic Molecule Approach to Multiorbital Topology
Maxim Mazanov, Diego Román-Cortés, Gabriel Cáceres-Aravena, Christofer Cid, Maxim A. Gorlach, and Rodrigo A. Vicencio

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00728

[ASAP] Gate-Tunable Quantum Acoustoelectric Transport in Graphene
Yicheng Mou, Haonan Chen, Jiaqi Liu, Qing Lan, Jiayu Wang, Chuanxin Zhang, Yuxiang Wang, Jiaming Gu, Tuoyu Zhao, Xue Jiang, Wu Shi, and Cheng Zhang

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00774

[ASAP] Proposed Quantum Twisting Scanning Probe Microscope over Twisted Bilayer Graphene
Yifan Ke, Lingyun Wan, Xinming Qin, Wei Hu, and Jinlong Yang

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00205

[ASAP] Large and Pressure-Dependent c-Axis Piezoresistivity of Highly Oriented Pyrolytic Graphite near Zero Pressure
Bingjie Wang, Juyao Li, Zheng Fang, Yifan Jiang, Shuo Li, Fangyuan Zhan, Zhaohe Dai, Qing Chen, and Xianlong Wei

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00687

[ASAP] Intrinsic Self-Trapped Excitons in Graphitic Carbon Nitride
Junhong Yu, Yunhu Wang, Yubu Zhou, Wenhui Fang, Baiquan Liu, and Jun Xing

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.4c00238

Found 8 papers in acs-nano
Date of feed: Mon, 08 Apr 2024 13:11:57 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] Dynamic Insights into the Growth Mechanisms of 2D Covalent Organic Frameworks on Graphene Surfaces
Weizhe Hao, Chao Sui, Gong Cheng, Junjiao Li, Linlin Miao, Guoxin Zhao, Yuna Sang, Jiaxuan Li, Chenxi Zhao, Yichen Zhou, Zifu Zang, Yushun Zhao, Xiaodong He, and Chao Wang

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c11787

[ASAP] Direct Assessment of Defective Regions in Monolayer MoS2 Field-Effect Transistors through In Situ Scanning Probe Microscopy Measurements
Albert Minj, Vivek Mootheri, Sreetama Banerjee, Ankit Nalin Mehta, Jill Serron, Thomas Hantschel, Inge Asselberghs, Ludovic Goux, Gouri Sankar Kar, Marc Heyns, and Dennis H. C. Lin

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ACS Nano
DOI: 10.1021/acsnano.4c03080

[ASAP] In Operando Study of Charge Modulation in MoS2 Transistors by Excitonic Reflection Microscopy
Nathan Ullberg, Arianna Filoramo, Stéphane Campidelli, and Vincent Derycke

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c09337

[ASAP] Multi-Stimuli-Responsive, Topology-Regulated, and Lignin-Based Nano/Microcapsules from Pickering Emulsion Templates for Bidirectional Delivery of Pesticides
Bin Yu, Jingli Cheng, Yun Fang, Zhengang Xie, Qiuyu Xiong, Haonan Zhang, Wenxuan Shang, Frederik R. Wurm, Wenlong Liang, Fanglin Wei, and Jinhao Zhao

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c11621

[ASAP] Effect of Interlayer Bonding on Superlubric Sliding of Graphene Contacts: A Machine-Learning Potential Study
Penghua Ying, Amir Natan, Oded Hod, and Michael Urbakh

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c13099

[ASAP] Multilevel Heterogeneous Interfaces Enhanced Polarization Loss of 3D-Printed Graphene/NiCoO2/Selenides Aerogels for Boosting Electromagnetic Energy Dissipation
Xiaoyan Liu, Wenle Ma, Tianyue Yang, Zhengrong Qiu, Jianbin Wang, Yuhao Li, Yang Wang, and Yi Huang

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.4c00193

[ASAP] Topological Quantum Well States in Pb/Sb Thin-Film Heterostructures
Yao Li, Yang-hao Chan, Joseph A. Hlevyack, John W. Bowers, Mei-Yin Chou, and Tai-Chang Chiang

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.4c00724

[ASAP] Exciton Dynamics of TiOPc/WSe2 Heterostructure
Shuo Xiong, Yuwei Wang, Jialong Yao, Jing Xu, and Mingsheng Xu

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.4c00946

Found 1 papers in nat-comm

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

Nonlinear optical diode effect in a magnetic Weyl semimetal
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