Found 25 papers in cond-mat
Date of feed: Thu, 14 Dec 2023 01:30:00 GMT

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

Observation of dynamic non-Hermitian skin effects. (arXiv:2312.07564v1 [quant-ph])
Zhen Li, Li-Wei Wang, Xulong Wang, Zhi-Kang Lin, Guancong Ma, Jian-Hua Jiang

Non-Hermitian effects have emerged as a new paradigm for the manipulation of phases of matter that profoundly changes our understanding of non-equilibrium systems, introducing novel concepts such as exceptional points and spectral topology, as well as exotic phenomena such as non-Hermitian skin effects (NHSEs). Most existing studies, however, focus on non-Hermitian eigenstates, whereas dynamic properties of non-Hermitian systems have been discussed only very recently, predicting unexpected phenomena such as wave self-healing, chiral Zener tunneling, and the dynamic NHSEs that are not yet confirmed in experiments. Here, we report the first experimental observation of rich non-Hermitian skin dynamics using tunable one-dimensional nonreciprocal double-chain mechanical systems with glide-time symmetry. Remarkably, dynamic NHSEs are observed with various dynamic behaviors in different dynamic phases, revealing the intriguing nature of these phases that can be understood via the generalized Brillouin zone and the related concepts. Moreover, the observed tunable non-Hermitian skin dynamics and amplifications, the bulk unidirectional wave propagation, and the boundary wave trapping provide promising ways to guide, trap, and amplify waves in a controllable and robust way. Our findings unveil the fundamental aspects and open a new pathway toward non-Hermitian dynamics, which will fertilize the study of non-equilibrium phases of matter and give rise to novel applications in information processing.

Superconducting quantum criticality and the anomalous scaling: A nonlinear relativistic equation. (arXiv:2312.07567v1 [cond-mat.supr-con])
Yong Tao

By using the Landau-Ginzburg-Wilson paradigm, we show that, near a quantum critical point (QCP), Cooper pairs at zero temperature would obey a nonlinear relativistic equation, where the imaginary time emerges as a novel dimension. This relativistic equation is applicable to certain superconductors at zero temperature for which the Faber-Pippard coherence length formula holds at and above the upper critical dimension. Here, we further show that the relativistic equation leads to a testable prediction in the vicinity of the QCP $T_c=0$, with $T_c$ being the transition temperature. That is, for 2D overdoped (clean) superconducting films, when the parameter $T_c/(c_0v_F)$ is lower than a characteristic scale, the Lorentz symmetry of relativistic equation arouses an anomalous scaling $\xi_0 \propto T_c^{-1.34}$, where $\xi_0$ denotes the zero-temperature coherence length, $v_F$ denotes the Fermi velocity, and $c_0$ denotes the Faber-Pippard coefficient. However, when the parameter $T_c/(c_0v_F)$ is large enough, the Lorentz symmetry may be broken so that the Faber-Pippard scaling $\xi_0 \propto T_c^{-1}$ is restored.

From Microscale Variations to Macroscopic Effects: Directional Actuation, Phase Transition, and Negative Compressibility in Microfiber-Based Shape-Morphing Networks. (arXiv:2312.07568v1 [cond-mat.soft])
Shiran Ziv Sharabani, Elad Livnat, Maia Abuchalja, Noa Haphiloni, Nicole Edelstein-Pardo, Tomer Reuveni, Maya Molco, Amit Sitt

Two-dimensional shape-morphing networks are common in biological systems and have garnered attention due to their nontrivial physical properties that emanate from their cellular nature. Here, we present the fabrication and characterization of inhomogeneous shape-morphing networks composed of thermoresponsive microfibers. By strategically positioning fibers with varying responses, we construct networks that exhibit directional actuation. The individual segments within the network display either a linear extension or buckling upon swelling, depending on their radius and length, and the transition between these morphing behaviors resembles Landau's second-order phase transition. The microscale variations in morphing behaviors are translated into observable macroscopic effects, wherein regions undergoing linear expansion retain their shape upon swelling, whereas buckled regions demonstrate negative compressibility and shrink. Manipulating the macroscale morphing by adjusting the properties of the fibrous microsegments offers a means to modulate and program morphing with mesoscale precision and unlocks novel opportunities for developing programmable microscale soft robotics and actuators.

Wigner Molecular Crystals from Multi-electron Moir\'e Artificial Atoms. (arXiv:2312.07607v1 [cond-mat.mes-hall])
Hongyuan Li, Ziyu Xiang, Aidan P. Reddy, Trithep Devakul, Renee Sailus, Rounak Banerjee, Takashi Taniguchi, Kenji Watanabe, Sefaattin Tongay, Alex Zettl, Liang Fu, Michael F. Crommie, Feng Wang

Semiconductor moir\'e superlattices provide a versatile platform to engineer new quantum solids composed of artificial atoms on moir\'e sites. Previous studies have mostly focused on the simplest correlated quantum solid - the Fermi-Hubbard model - where intra-atom interactions are simplified to a single onsite repulsion energy U. These studies have revealed novel quantum phases ranging from Mott insulators to quantum anomalous Hall insulators at a filling of one electron per moir\'e unit cell. New types of quantum solids should arise at even higher filling factors where the multi-electron configuration of moir\'e artificial atoms provides new degrees of freedom. Here we report the experimental observation of Wigner molecular crystals emerging from multi-electron artificial atoms in twisted bilayer WS2 moir\'e superlattices. Moir\'e artificial atoms, unlike natural atoms, can host qualitatively different electron states due to the interplay between quantized energy levels and Coulomb interactions. Using scanning tunneling microscopy (STM), we demonstrate that Wigner molecules appear in multi-electron artificial atoms when Coulomb interactions dominate. Three-electron Wigner molecules, for example, are seen to exhibit a characteristic trimer pattern. The array of Wigner molecules observed in a moir\'e superlattice comprises a new crystalline phase of electrons: the Wigner molecular crystal. We show that these Wigner molecular crystals are highly tunable through mechanical strain, moir\'e period, and carrier charge type. Our study presents new opportunities for exploring quantum phenomena in moir\'e quantum solids composed of multi-electron artificial atoms.

Van-Hove tuning of Fermi surface instabilities through compensated metallicity. (arXiv:2312.07653v1 [cond-mat.str-el])
Hendrik Hohmann, Matteo Dürrnagel, Matthew Bunney, Tilman Schwemmer, Titus Neupert, Stephan Rachel, Ronny Thomale

Van-Hove (vH) singularities in the vicinity of the Fermi level facilitate the emergence of electronically mediated Fermi surface instabilities. This is because they provide a momentum-localized enhancement of density of states enhancing selective electronic scattering channels. High-temperature topological superconductivity has been argued for in graphene at vH filling which, however, has so far proven inaccessible due to the demanded large doping from pristine half filling. We propose compensated metallicity as a path to unlock vH-driven pairing close to half filling in an electronic honeycomb lattice model. It is enabled through the strong breaking of chiral symmetry from intra-sublattice hybridization, leading to the emergence of a hole pocket (hp) nearby the van-Hove points $M$ at the Brillouin zone boundary and an electron pocket (ep) around the zone center $\Gamma$. While the ep is radially symmetric and barely contributing to the electronic ordering selection, the hp is dominated by its vH signature and yields electronic order at elevated scales.

Lorentz invariance violation and the CPT-odd electromagnetic response of a tilted anisotropic Weyl semimetal. (arXiv:2312.07791v1 [hep-th])
Andrés Gómez, R. Martínez von Dossow, A. Martín-Ruiz, Luis F. Urrutia

We derive the electromagnetic response of a particular fermionic sector in the minimal QED contribution to the Standard Model Extension (SME), which can be physically realized in terms of a model describing a tilted and anisotropic Weyl semimetal (WSM). The contact is made through the identification of the Dirac-like Hamiltonian resulting from the SME with that corresponding to the WSM in the linearized tight-binding approximation. We first calculate the effective action by computing the non-perturbative vacuum polarization tensor using thermal field theory techniques, focusing upon the corrections at finite chemical potential and zero temperature. Next, we confirm our results by a direct calculation of the anomalous Hall current within a chiral kinetic theory approach.

In an ideal Dirac cone picture of the WSM (isotropic and non-tilted) such response is known to be governed by axion electrodynamics, with the space-time dependent axion angle $\Theta (\mathbf{r},t) = 2 (\mathbf{b} \cdot \mathbf{r} - b _{0} t)$, being $2 \mathbf{b}$ and $2b _{0}$ the separation of the Weyl nodes in momentum and energy, respectively. In this paper we demonstrate that the node tilting and the anisotropies induce novel corrections at a finite density which however preserve the structure of the axionic field theory. We apply our results to the ideal Weyl semimetal $\mathrm{EuCd}_{2}\mathrm{As}_{2}$ and to the highly anisotropic and tilted monopnictide $\mathrm{TaAs}$.

Current-induced near-field radiative energy, linear-momentum, and angular-momentum transfer. (arXiv:2312.07954v1 [physics.optics])
Huimin Zhu, Gaomin Tang, Lei Zhang, Jun Chen

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

Atomic topological quantum matter using synthetic dimensions. (arXiv:2312.07984v1 [cond-mat.quant-gas])
Aurélien Fabre, Sylvain Nascimbene

The realization of topological states of matter in ultracold atomic gases is currently the subject of intense experimental activity. Using a synthetic dimension, encoded in a non-spatial degree of freedom, can greatly simplify the simulation of gauge fields and give access to exotic topological states. We review here recent advances in the field and discuss future perspectives for interacting systems.

Tunneling through ABC-ABA-ABC trilayer graphene junction. (arXiv:2312.08046v1 [cond-mat.mes-hall])
Abderrahim El Mouhafid, Mouhamadou Hassane Saley, Ahmed Jellal

The electronic tunneling properties of trilayer graphene (TLG) are significantly influenced by the specific stacking order. To illustrate this stacking influence, we investigate the transport properties of a p-n-p junction formed with ABC-ABA-ABC stacking TLG. Utilizing the transfer matrix method and considering continuity conditions at the junction boundaries, we establish transmission, reflection probabilities, and conductance. Remarkably, electron transport through the ABC-ABA-ABC junction demonstrates Klein tunneling, resulting in high conductance even in the absence of a potential barrier $V_0$. This phenomenon is attributed to the effective barrier induced by our stacking, facilitating the passage of a maximum number of electrons. However, the presence of $V_0$ diminishes Klein tunneling, leading to conductance minima. Furthermore, we reveal that the interlayer bias $\delta$ causes hybridization of the linear and parabolic bands of ABA-TLG in the junction, reducing resonances. In cases where $\delta\neq0$ and $V_0\neq0$, a suppression of the gap is observed, contrary to the results obtained in ABC tunneling studies where a gap exists.

Purely elastic turbulence in pressure-driven channel flows. (arXiv:2312.08091v1 [physics.flu-dyn])
Martin Lellep, Moritz Linkmann, Alexander Morozov

Solutions of long, flexible polymer molecules are complex fluids that simultaneously exhibit fluid-like and solid-like behaviour. When subjected to an external flow, dilute polymer solutions exhibit elastic turbulence - a unique, chaotic flow state absent in Newtonian fluids, like water. Unlike its Newtonian counterpart, elastic turbulence is caused by polymer molecules stretching and aligning in the flow, and can occur at vanishing inertia. While experimental realisations of elastic turbulence are well-documented, there is currently no understanding of its mechanism. Here, we present large-scale direct numerical simulations of elastic turbulence in pressure-driven flows through straight channels. We demonstrate that the transition to elastic turbulence is sub-critical, giving rise to spot-like flow structures that, further away from the transition, eventually spread throughout the domain. We provide evidence that elastic turbulence is organised around unstable coherent states that are localised close to the channel midplane.

Understanding the Role of Four-Phonon Scattering in the Lattice Thermal Transport of Monolayer MoS$_{2}$. (arXiv:2312.08219v1 [cond-mat.mtrl-sci])
Saumen Chaudhuri, Amrita Bhattacharya, A. K. Das, G. P. Das, B. N. Dev

In the calculations of lattice thermal conductivity ($\kappa_{\text{L}}$), vital contributions stemming from four-phonon scattering are often neglected. The significance of four-phonon scattering in the thermal transport properties of monolayer (ML) MoS$_{2}$ has been unraveled using first-principles calculations combined with the Boltzmann transport equation. If only three-phonon scattering processes are considered then the $\kappa_{\text{L}}$ is found to be significantly overestimated ($\sim$ 115.8 Wm$^{-1}$K$^{-1}$ at 300 K). With the incorporation of the four-phonon scattering processes, the $\kappa_{\text{L}}$ reduces to 24.6 Wm$^{-1}$K$^{-1}$, which is found to be closer to the experimentally measured $\kappa_{\text{L}}$ of 34.5 Wm$^{-1}$K$^{-1}$. Four-phonon scattering significantly impacts the carrier lifetime ($\tau$) of the low-energy out-of-plane acoustic mode (ZA) phonons and thereby, suppresses its contribution in $\kappa_{\text{L}}$ from 64% (for three-phonon scattering) to 16% (for both three- and four-phonon scatterings). The unusually high four-phonon scattering rate ($\tau_{4}^{-1}$) of the ZA phonons is found to result from the simultaneous effect of the acoustic-optical frequency gap, strong anharmonicity, and the reflection symmetry imposed selection rule. The strong coupling between the quadratic dispersion of the ZA mode and the $\tau_{4}^{-1}$ is discovered by the application of mechanical strain. The strain induced increase in the linearity of the ZA mode dispersion dramatically reduces the significance of the four-phonon scattering in the strained ML-MoS$_{2}$, both qualitatively and quantitatively. These conclusions will provide significant insights into the thermal transport phenomena in ML-MoS$_{2}$, as well as any other 2D material.

Robust Dipolar Layers between Organic Semiconductors and Silver for Energy-Level Alignment. (arXiv:2312.08233v1 [cond-mat.mtrl-sci])
Tomáš Krajňák, Veronika Stará, Pavel Procházka, Jakub Planer, Tomáš Skála, Matthias Blatnik, Jan Čechal

The interface between a metal electrode and an organic semiconductor (OS) layer has a defining role in the properties of the resulting device. To obtain a desired performance, interlayers are introduced to modify the adhesion and growth of OS and enhance the efficiency of charge transport through the interface. However, the employed interlayers face common challenges, including a lack of electric dipoles to tune the mutual position of energy levels, being too thick for efficient electronic transport, or being prone to intermixing with subsequently deposited OS layers. Here, we show that monolayers of 1,3,5-tris(4 carboxyphenyl)benzene (BTB) with fully deprotonated carboxyl group on silver substrates form a compact layer resistant to intermixing while mediating energy level alignment and showing a large insensitivity to substrate termination. Employing a combination of surface-sensitive techniques, i.e., low-energy electron microscopy and diffraction, X-ray photoelectron spectroscopy, and scanning tunneling microscopy, we have comprehensively characterized the compact layer and proven its robustness against mixing with the subsequently deposited organic semiconductor layer. DFT calculations show that the robustness arises from a strong interaction of carboxylate groups with the Ag surface, and thus, the BTB in the first layer is energetically favored. Synchrotron radiation photoelectron spectroscopy shows that this layer displays considerable electrical dipoles that can be utilized for work function engineering and electronic alignment of molecular frontier orbitals with respect to the substrate Fermi level. Our work thus provides a widely applicable molecular interlayer and general insights necessary for engineering of charge injection layers for efficient organic electronics.

Hydrodynamics and instabilities of relativistic superfluids at finite superflow. (arXiv:2312.08243v1 [hep-th])
Daniel Areán, Blaise Goutéraux, Eric Mefford, Filippo Sottovia

We study the linear response of relativistic superfluids with a non-zero superfluid velocity. For sufficiently large superflow, an instability develops via the crossing of a pole of the retarded Green's functions to the upper half complex frequency plane. We show that this is caused by a local thermodynamic instability, i.e. when an eigenvalue of the static susceptibility matrix (the second derivatives of the free energy) diverges and changes sign. The onset of the instability occurs when $\partial_{\zeta}(n_s\zeta)=0$, with $\zeta$ the norm of the superfluid velocity and $n_s$ the superfluid density. The Landau instability for non-relativistic superfluids such as Helium 4 also coincides with the non-relativistic version of this criterion. We then turn to gauge/gravity duality and show that this thermodynamic instability criterion applies equally well to strongly-coupled superfluids. In passing, we compute holographically a number of transport coefficients parametrizing deviations out-of-equilibrium in the hydrodynamic regime and demonstrate that the gapless quasinormal modes of the dual planar black hole match those predicted by superfluid hydrodynamics.

Topological entanglement entropy for torus knot bipartitions and the Verlinde-like formulas. (arXiv:2312.08348v1 [cond-mat.str-el])
Chih-Yu Lo, Po-Yao Chang

The topological R\'enyi and entanglement entropies depend on the bipartition of the manifold and the choice of the ground states. However, these entanglement quantities remain invariant under a coordinate transformation when the bipartition also undergoes the same transformation. In the context of topological quantum field theories, these coordinate transformations reduce to representations of the mapping class group on the manifold of the Hilbert space. We employ this invariant property of the R\'enyi and entanglement entropies under coordinate transformations for TQFTs in (2 + 1) dimensions on a torus with various bipartitions. By utilizing the replica trick and the surgery method to compute the topological R\'enyi and entanglement entropies, the invariant property results in Verlinde-like formulas. Furthermore, for the bipartition with interfaces as two non-intersecting torus knots, an $SL(2, \mathbb{Z})$ transformation can untwist the torus knots, leading to a simple bipartition with an effective ground state. This invariant property allows us to demonstrate that the topological entanglement entropy has a lower bound $-2 \ln D$, where $D$ is the total quantum dimensions of the system.

One-step replica symmetry breaking of random regular NAE-SAT I. (arXiv:2011.14270v3 [math.PR] UPDATED)
Danny Nam, Allan Sly, Youngtak Sohn

In a broad class of sparse random constraint satisfaction problems(CSP), deep heuristics from statistical physics predict that there is a condensation phase transition before the satisfiability threshold, governed by one-step replica symmetry breaking(1RSB). In fact, in random regular k-NAE-SAT, which is one of such random CSPs, it was verified \cite{ssz22} that its free energy is well-defined and the explicit value follows the 1RSB prediction. However, for any model of sparse random CSP, it has been unknown whether the solution space indeed condenses on O(1) clusters according to the 1RSB prediction. In this paper, we give an affirmative answer to this question for the random regular k-NAE-SAT model. Namely, we prove that with probability bounded away from zero, most of the solutions lie inside a bounded number of solution clusters whose sizes are comparable to the scale of the free energy. Furthermore, we establish that the overlap between two independently drawn solutions concentrates precisely at two values. Our proof is based on a detailed moment analysis of a spin system, which has an infinite spin space that encodes the structure of solution clusters. We believe that our method is applicable to a broad range of random CSPs in the 1RSB universality class.

Pair correlation function based on Voronoi topology. (arXiv:2210.09731v2 [cond-mat.dis-nn] UPDATED)
Vasco M. Worlitzer, Gil Ariel, Emanuel A. Lazar

The pair correlation function (PCF) has proven an effective tool for analyzing many physical systems due to its simplicity and its applicability to simulated and experimental data. However, as an averaged quantity, the PCF can fail to capture subtle structural differences in particle arrangements, even when those differences can have a major impact on system properties. Here, we use Voronoi topology to introduce a discrete version of the PCF that highlights local inter-particle topological configurations. The advantages of the Voronoi PCF are demonstrated in several examples including crystalline, hyperuniform, and active systems showing clustering and giant number fluctuations.

Renormalisation Group Flows of Deformed SYK Models. (arXiv:2212.04944v2 [hep-th] UPDATED)
Dionysios Anninos, Damián A. Galante, Sameer U. Sheorey

We explore computationally tractable deformations of the SYK model. The deformed theories are described by the sum of two SYK Hamiltonians with differing numbers, $q$ and $\tilde{q}$, of interacting fermions. In the large $N$ limit, employing analytic and numerical tools, we compute finite temperature correlation functions and thermodynamic quantities. We identify a novel analytically solvable model in the large $q$ limit. We find that, under certain circumstances, the thermal RG flow in the strongly coupled infrared phase exhibits two regions of linear-in-temperature entropy, which we interpret in terms of Schwarzian actions. Using conformal perturbation theory we compute the leading relevant correction away from the intermediate near-conformal fixed point. Holographic spacetimes in two spacetime dimensions that reproduce the thermodynamics of the microphysical theory are discussed. These are flow geometries that interpolate between two Euclidean near-AdS$_2$ spacetimes with different radii. The Schwarzian soft mode corresponding to the AdS$_2$ region in the deep interior resides entirely within the geometric regime.

Anatomy of topological Anderson transitions. (arXiv:2301.04565v2 [cond-mat.dis-nn] UPDATED)
Hao Zhang, Alex Kamenev

We study mesoscopic signatures of the topological Anderson transitions in topological disordered chains. To this end we introduce an integer-valued sample-specific definition of the topological index in finite size systems. Its phase diagram exhibits a fascinating structure of intermittent topological phases, dubbed topological islands. Their existence is rooted in the real zeros of the underlying random polynomial. Their statistics exhibits finite-size scaling, pointing to the location of the bulk topological Anderson transition. While the average theories in AIII and BDI symmetry classes are rather similar, the corresponding patterns of topological islands and their statistics are qualitatively different. We also discuss observable signatures of sharp topological transitions in mesoscopic systems, such as persistent currents and entanglement spectra.

Tight-binding model with sublattice-asymmetric spin-orbit coupling for square-net nodal line Dirac semimetals. (arXiv:2304.03438v3 [cond-mat.mtrl-sci] UPDATED)
Gustavo S. Orozco-Galvan, Amador Garcia-Fuente, Salvador Barraza-Lopez

We study a 4-orbital tight-binding (TB) model for ZrSiS from the square sublattice generated by the Si atoms. After studying three other alternatives, we endow such model with a new effective spin-orbit coupling (SOC) consistent with {\em ab initio} dispersions around the Fermi energy ($E_F$) in four systematic steps: (1) We calculate the electronic dispersion of bulk ZrSiS using an implementation of density-functional theory (DFT) based on numeric atomic orbitals [{\em J. Phys.: Condens. Matter} {\bf 14}, 2745 (2002)] in which on-site and off-site SOC can be told apart. As a result, we determine that local SOC-induced band gaps around $E_F$ are predominantly created by the on-site contribution. (2) Gradually reducing the atomic basis set size, we then create an electronic band structure with 16 orbitals per unit cell (u.c.) which retains the qualitative features of the dispersion around $E_F$, including SOC-induced band gaps. (3) Zr is the heaviest element on this compound and it has a non-negligible contribution to the electronic dispersion around $E_F$; we show that it provides the strongest contribution to the SOC-induced band gap. (4) Using L\"{o}wdin partitioning approach, we project the effect of SOC onto the 4-orbital Hamiltonian. This way, we facilitate an effective SOC interaction that was explicitly informed by {\em ab initio} input.

Gate-Defined Topological Josephson Junctions in Bernal Bilayer Graphene. (arXiv:2304.11807v3 [cond-mat.mes-hall] UPDATED)
Ying-Ming Xie, Étienne Lantagne-Hurtubise, Andrea F. Young, Stevan Nadj-Perge, Jason Alicea

Recent experiments on Bernal bilayer graphene (BLG) deposited on monolayer WSe$_2$ revealed robust, ultra-clean superconductivity coexisting with sizable induced spin-orbit coupling. Here we propose BLG/WSe$_2$ as a platform to engineer gate-defined planar topological Josephson junctions, where the normal and superconducting regions descend from a common material. More precisely, we show that if superconductivity in BLG/WSe$_2$ is gapped and emerges from a parent state with inter-valley coherence, then Majorana zero modes can form in the barrier region upon applying weak in-plane magnetic fields. Our results spotlight a potential pathway for `internally engineered' topological superconductivity that minimizes detrimental disorder and orbital-magnetic-field effects.

Message-Passing Neural Quantum States for the Homogeneous Electron Gas. (arXiv:2305.07240v3 [quant-ph] UPDATED)
Gabriel Pescia, Jannes Nys, Jane Kim, Alessandro Lovato, Giuseppe Carleo

We introduce a message-passing-neural-network-based wave function Ansatz to simulate extended, strongly interacting fermions in continuous space. Symmetry constraints, such as continuous translation symmetries, can be readily embedded in the model. We demonstrate its accuracy by simulating the ground state of the homogeneous electron gas in three spatial dimensions at different densities and system sizes. With orders of magnitude fewer parameters than state-of-the-art neural-network wave functions, we demonstrate better or comparable ground-state energies. Reducing the parameter complexity allows scaling to $N=128$ electrons, previously inaccessible to neural-network wave functions in continuous space, enabling future work on finite-size extrapolations to the thermodynamic limit. We also show the Ansatz's capability of quantitatively representing different phases of matter.

Majorana zero modes in gate-defined germanium hole nanowires. (arXiv:2305.14313v2 [cond-mat.mes-hall] UPDATED)
Katharina Laubscher, Jay D. Sau, Sankar Das Sarma

We theoretically study gate-defined one-dimensional channels in planar Ge hole gases as a potential platform for non-Abelian Majorana zero modes. We model the valence band holes in the Ge channel by adding appropriate confinement potentials to the 3D Luttinger-Kohn Hamiltonian, additionally taking into account a magnetic field applied parallel to the channel, an out-of-plane electric field, as well as the effect of compressive strain in the parent quantum well. Assuming that the Ge channel is proximitized by an $s$-wave superconductor (such as, e.g., Al) we calculate the topological phase diagrams for different channel geometries, showing that sufficiently narrow Ge hole channels can indeed enter a topological superconducting phase with Majorana zero modes at the channel ends. We estimate the size of the topological gap and its dependence on various system parameters such as channel width, strain, and the applied out-of-plane electric field, allowing us to critically discuss under which conditions Ge hole channels may manifest Majorana zero modes. Since ultra-clean Ge quantum wells with hole mobilities exceeding one million and mean-free paths on the order of many microns already exist, gate-defined Ge hole channels may be able to overcome some of the problems caused by the presence of substantial disorder in more conventional Majorana platforms.

Triple-Well Charge Density Wave Transition Driven by Cooperation between Peierls-like Effect and Antiferromagnetic Order in FeGe. (arXiv:2307.10565v2 [cond-mat.mtrl-sci] UPDATED)
Binhua Zhang, Junyi Ji, Changsong Xu, Hongjun Xiang

Kagome materials provide a promising platform to explore intriguing correlated phenomena including magnetism, charge density wave (CDW), and nontrivial band topology. Recently, a CDW order was observed in antiferromagnetic kagome metal FeGe, sparking enormous research interests in intertwining physics of CDW and magnetism. Two of the core questions are (i) what are the driving forces of the CDW transition in FeGe and (ii) whether magnetism play a critical role in the transition. Such questions are critical as conventional mechanisms of van Hove singularities and Fermi surface nesting fail to explain the stable pristine phase, as well as the role of magnetism. Here, supported by density functional theory and tight-binding models, we unravel the triple-well CDW energy landscape of FeGe, indicating that both the pristine and CDW phases are locally stable. We point out that an entire downward shift of Ge band, instead of the previously proposed Fe bands, competes with the lattice distortion energy, driving the triple-well CDW transition. It is indeed a cooperation between the Peierls-like effect and the Fermi energy pinning phenomenon, which is distinct from the conventional Peierls effect that drives a double-well transition. Moreover, we demonstrate that the antiferromagnetic order also plays a critical role in driving the CDW transition, through weakening the Fe-Ge hybridization by exchange splitting and lowering the position of Ge-bands with respect to the Fermi energy. Our work thus not only deepens the understanding of the CDW mechanism in FeGe, but also indicates an intertwined connection between the emergent magnetism and CDW in kagome materials.

Landau-level spectrum and the effect of spin-orbit coupling in monolayer graphene on transition metal dichalcogenides. (arXiv:2310.00686v2 [cond-mat.mes-hall] UPDATED)
Qing Rao, Hongxia Xue, Dong-Keun Ki

In graphene on transition metal dichalcogenides, proximity-induced Rashba and spin-valley Zeeman SOCs can coexist that modify graphene's electronic band differently. Here, we show that the Landau levels (LLs) are also affected by these SOCs distinctively enough to estimate their relative strengths from the Landau fan diagram. Using a simple theoretical model, we calculated the LL spectrums of graphene for different SOC strengths, and found that when the total SOC is strong enough (i.e., when it is comparable to the half of the energy gap between the LLs of an intrinsic graphene), the corresponding LLs will split and cross with others depending sensitively on the relative strengths of the SOC terms. To demonstrate how one can use it to estimate the relative SOC strengths, we first identified the four key features that are well separated from the complex background and can be compared with experiment directly, and used them to show that in our sample, the Rashba SOC is stronger than the spin-valley Zeeman SOC that is consistent with other spectroscopic measurements. Our study therefore provides a simple and practical strategy to analyze the LL spectrum in graphene with SOC before carrying out more in-depth measurements.

A Machine Learning Approach to Robustly Determine Director Fields and Analyze Defects in Active Nematics. (arXiv:2310.12449v2 [cond-mat.soft] UPDATED)
Yunrui Li, Zahra Zarei, Phu N. Tran, Yifei Wang, Aparna Baskaran, Seth Fraden, Michael F. Hagan, Pengyu Hong

Active nematics are dense systems of rodlike particles that consume energy to drive motion at the level of the individual particles. They exist in natural systems like biological tissues and artificial materials such as suspensions of self-propelled colloidal particles or synthetic microswimmers. Active nematics have attracted significant attention in recent years due to their spectacular nonequilibrium collective spatiotemporal dynamics, which may enable applications in fields such as robotics, drug delivery, and materials science. The director field, which measures the direction and degree of alignment of the local nematic orientation, is a crucial characteristic of active nematic and is essential for studying topological defects. However, determining the director field is a significant challenge in many experimental systems. Although director fields can be derived from images of active nematics using traditional imaging processing methods, the accuracy of such methods are highly sensitive to the settings of the algorithms. These settings must be tuned from image-to-image due to experimental noise, intrinsic noise of the imaging technology, and perturbations caused by changes in experimental conditions. This sensitivity currently limits automatic analysis of active nematics. To address this, we developed a machine learning model for extracting reliable director fields from raw experimental images, which enables accurate analysis of topological defects. Application of the algorithm to experimental data demonstrates that the approach is robust and highly generalizable to experimental settings that are different from those in the training data. It could be a promising tool for investigating active nematics and may be generalized to other active matter systems.

Found 6 papers in prb
Date of feed: Thu, 14 Dec 2023 04:16:59 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)

Superconductivity and critical fields of tellurium single crystal under high pressure
Lingxiao Zhao, Cuiying Pei, Juefei Wu, Yi Zhao, Qi Wang, Bangshuai Zhu, Changhua Li, Weizheng Cao, and Yanpeng Qi
Author(s): Lingxiao Zhao, Cuiying Pei, Juefei Wu, Yi Zhao, Qi Wang, Bangshuai Zhu, Changhua Li, Weizheng Cao, and Yanpeng Qi

Tellurium (Te) is one of the $p$-orbital chalcogens, which shows attractive physical properties at ambient pressure. Here, we systematically investigate both structural and electronic evolution of Te single crystal under high pressure up to 40 GPa. The pressure dependence of the experimental Raman s…

[Phys. Rev. B 108, 214518] Published Wed Dec 13, 2023

Universal conductivity at a two-dimensional superconductor-insulator transition: The effects of quenched disorder and Coulomb interaction
Chao-Jung Lee and Michael Mulligan
Author(s): Chao-Jung Lee and Michael Mulligan

We calculate the zero-temperature dc electrical conductivity in the collisionless $ℏω/{k}_{B}T→∞$ limit at superconductor-insulator transitions in the $(2+1)\mathrm{d}$ XY model universality class. We use a dual model consisting of a single Dirac fermion at zero density, coupled to a Chern-Simons ga…

[Phys. Rev. B 108, 235142] Published Wed Dec 13, 2023

One-half topological number in entangled quantum physics
Karyn Le Hur
Author(s): Karyn Le Hur

A topological phase can be engineered in quantum physics from the Bloch sphere of a spin-1/2 showing a hedgehog structure as a result of a radial magnetic field. We elaborate on a relation between the formation of an entangled wavefunction at one pole, in a two-spins model, and an interesting pair o…

[Phys. Rev. B 108, 235144] Published Wed Dec 13, 2023

Dynamical simulation of the injection of vortices into a Majorana edge mode
I. M. Flór, A. Donís-Vela, C. W. J. Beenakker, and G. Lemut
Author(s): I. M. Flór, A. Donís-Vela, C. W. J. Beenakker, and G. Lemut

The chiral edge modes of a topological superconductor can transport fermionic quasiparticles with Abelian exchange statistics, but they can also transport non-Abelian anyons: edge vortices bound to a $π$-phase domain wall that propagates along the boundary. A pair of such edge vortices is injected b…

[Phys. Rev. B 108, 235309] Published Wed Dec 13, 2023

Flat bands and electronic localization in twisted bilayer graphene nanoribbons
Elias Andrade, Pierre A. Pantaleón, Francisco Guinea, and Gerardo G. Naumis
Author(s): Elias Andrade, Pierre A. Pantaleón, Francisco Guinea, and Gerardo G. Naumis

In an infinite twisted bilayer graphene lattice, flat bands emerge, representing electrons localized at the AA stacking regions. This study investigates the behavior of these bands when dealing with incomplete moiré supercells in twisted bilayer graphene nanoribbons. The findings reveal a transition from dispersive to flat bands near charge neutrality as the supercell completeness varies. Moreover, it is observed that the microscopic edges can influence the energy of states localized at the AA regions near the borders.

[Phys. Rev. B 108, 235418] Published Wed Dec 13, 2023

Layer number and stacking order dependent thermal transport in molybdenum disulfide with sulfur vacancies
Ranjuna M K and Jayakumar Balakrishnan
Author(s): Ranjuna M K and Jayakumar Balakrishnan

Recent theoretical works on two-dimensional molybdenum disulfide (${\mathrm{MoS}}_{2}$) with sulfur vacancies predict that the suppression of thermal transport in ${\mathrm{MoS}}_{2}$ by point defects is more prominent in monolayers and becomes negligible as the layer number increases. Here, we inve…

[Phys. Rev. B 108, 245411] Published Wed Dec 13, 2023

Found 1 papers in prl
Date of feed: Thu, 14 Dec 2023 04:16:57 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)

Polariton Condensation in Gap-Confined States of Photonic Crystal Waveguides
F. Riminucci, A. Gianfrate, D. Nigro, V. Ardizzone, S. Dhuey, L. Francaviglia, K. Baldwin, L. N. Pfeiffer, D. Ballarini, D. Trypogeorgos, A. Schwartzberg, D. Gerace, and D. Sanvitto
Author(s): F. Riminucci, A. Gianfrate, D. Nigro, V. Ardizzone, S. Dhuey, L. Francaviglia, K. Baldwin, L. N. Pfeiffer, D. Ballarini, D. Trypogeorgos, A. Schwartzberg, D. Gerace, and D. Sanvitto

The development of patterned multiquantum well heterostructures in GaAs/AlGaAs waveguides has recently made it possible to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Polariton condensation was shown to occur above a saddle point of the two…

[Phys. Rev. Lett. 131, 246901] Published Wed Dec 13, 2023

Found 1 papers in prx
Date of feed: Thu, 14 Dec 2023 04:16:57 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)

Discovery of a Single-Band Mott Insulator in a van der Waals Flat-Band Compound
Shunye Gao et al.
Author(s): Shunye Gao et al.

The fundamental model for understanding Mott insulators is the single-band Hubbard model. An ideal realization of that model arises in Nb3Cl8, proving a powerful system for exploring Mott physics and other correlated states.

[Phys. Rev. X 13, 041049] Published Wed Dec 13, 2023

Found 1 papers in nano-lett
Date of feed: Wed, 13 Dec 2023 22:03:49 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] Excitonic Effects in Energy-Loss Spectra of Freestanding Graphene
Alberto Guandalini, Ryosuke Senga, Yung-Chang Lin, Kazu Suenaga, Andrea Ferretti, Daniele Varsano, Andrea Recchia, Paolo Barone, Francesco Mauri, Thomas Pichler, and Christian Kramberger

TOC Graphic

Nano Letters
DOI: 10.1021/acs.nanolett.3c03863

Found 1 papers in acs-nano
Date of feed: Wed, 13 Dec 2023 23:04:28 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] Spatiotemporal Observation of Quasi-Ballistic Transport of Electrons in Graphene
Ryan J. Scott, Pavel Valencia-Acuna, and Hui Zhao

TOC Graphic

ACS Nano
DOI: 10.1021/acsnano.3c08816

Found 2 papers in science-adv
Date of feed: Wed, 13 Dec 2023 20:00:18 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)

Plasma membrane nanodeformations promote actin polymerization through CIP4/CDC42 recruitment and regulate type II IFN signaling
Benjamin Ledoux, Natacha Zanin, Jinsung Yang, Vincent Mercier, Charlotte Coster, Christine Dupont-Gillain, David Alsteens, Pierre Morsomme, Henri-François Renard
Science Advances, Volume 9, Issue 50, December 2023.

Thermally generated spin current in the topological insulator Bi2Se3
Rakshit Jain, Max Stanley, Arnab Bose, Anthony R. Richardella, Xiyue S. Zhang, Timothy Pillsbury, David A. Muller, Nitin Samarth, Daniel C. Ralph
Science Advances, Volume 9, Issue 50, December 2023.

Found 1 papers in scipost

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)

$T \overline{T}$-Like Flows and $3d$ Nonlinear Supersymmetry, by Christian Ferko, Yangrui Hu, Zejun Huang, Konstantinos Koutrolikos, Gabriele Tartaglino-Mazzucchelli
< author missing >
Submitted on 2023-12-14, refereeing deadline 2024-01-19.