Found 58 papers in cond-mat
Date of feed: Tue, 01 Aug 2023 00:30:00 GMT

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Scaling transition of active turbulence from two to three dimensions. (arXiv:2307.15720v1 [cond-mat.soft])
Da Wei, Yaochen Yang, Xuefeng Wei, Ramin Golestanian, Ming Li, Fanlong Meng, Yi Peng

Turbulent flows are observed in low-Reynolds active fluids. They are intrinsically different from the classical inertial turbulence and behave distinctively in two- and three-dimensions. Understanding the behaviors of this new type of turbulence and their dependence on the system dimensionality is a fundamental challenge in non-equilibrium physics. We experimentally measure flow structures and energy spectra of bacterial turbulence between two large parallel plates spaced by different heights $H$. The turbulence exhibits three regimes as H increases, resulting from the competition of bacterial length, vortex size and H. This is marked by two critical heights ($H_0$ and $H_1$) and a $H^{0.5}$ scaling law of vortex size in the large-$H$ limit. Meanwhile, the spectra display distinct universal scaling laws in quasi-two-dimensional (2D) and three-dimensional (3D) regimes, independent of bacterial activity, length and $H$, whereas scaling exponents exhibit transitions in the crossover. To understand the scaling laws, we develop a hydrodynamic model using image systems to represent the effect of no-slip confining boundaries. This model predicts universal 1 and -4 scaling on large and small length scales, respectively, and -2 and -1 on intermediate length scales in 2D and 3D, respectively, which are consistent with the experimental results. Our study suggests a framework for investigating the effect of dimensionality on non-equilibrium self-organized systems.

Selective Manipulation and Tunneling Spectroscopy of Broken-Symmetry Quantum Hall States in a Hybrid-edge Quantum Point Contact. (arXiv:2307.15728v1 [cond-mat.mes-hall])
Wei Ren, Xi Zhang, Jaden Ma, Xihe Han, Kenji Watanabe, Takashi Taniguchi, Ke Wang

We present a device architecture of hybrid-edge and dual-gated quantum point contact. We demonstrate improved electrostatic control over the separation, position, and coupling of each broken-symmetry compressible strip in graphene. Via low-temperature magneto-transport measurement, we demonstrate selective manipulation over the evolution, hybridization, and transmission of arbitrarily chosen quantum Hall states in the channel. With gate-tunable tunneling spectroscopy, we characterize the energy gap of each symmetry-broken quantum Hall state with high resolution on the order of ~0.1 meV.

Magnetic Antiskyrmions in Two-Dimensional van der Waals Magnets Engineered by Layer Stacking. (arXiv:2307.15769v1 [cond-mat.mtrl-sci])
Kai Huang, Edward Schwartz, Ding-Fu Shao, Alexey A. Kovalev, Evgeny Y. Tsymbal

Magnetic skyrmions and antiskyrmions are topologically protected quasiparticles exhibiting a whirling spin texture in real space. Antiskyrmions offer some advantages over skyrmions as they are expected to have higher stability and can be electrically driven with no transverse motion. However, unlike the widely investigated skyrmions, antiskyrmions are rarely observed due to the required anisotropic Dzyaloshinskii-Moriya interaction (DMI). Here we propose to exploit the recently demonstrated van der Waals (vdW) assembly of two-dimensional (2D) materials that breaks inversion symmetry and creates conditions for anisotropic DMI. Using a 2D vdW magnet CrI${}_3$ as an example, we demonstrate, based on density functional theory (DFT) calculations, that this strategy is a promising platform to realize antiskyrmions. Polar layer stacking of two centrosymmetric magnetic monolayers of CrI${}_3$ efficiently lowers the symmetry, resulting in anisotropic DMI that supports antiskyrmions. The DMI is reversible by switching the ferroelectric polarization inherited from the polar layer stacking, offering the control of antiskyrmions by an electric field. Furthermore, we find that the magnetocrystalline anisotropy and DMI of CrI${}_3$ can be efficiently modulated by Mn doping, creating a possibility to control the size of antiskyrmions. Using atomistic spin dynamics simulations with the parameters obtained from our DFT calculations, we predict the formation of antiskyrmions in a Cr${}_{0.88}$Mn${}_{0.12}$I${}_3$ bilayer and switching their spin texture with polarization reversal. Our results open a new direction to generate and control magnetic antiskyrmions in 2D vdW magnetic systems.

Superconducting-Spin Reorientation in Spin-Triplet Multiple Superconducting Phases of UTe2. (arXiv:2307.15784v1 [cond-mat.supr-con])
Katsuki Kinjo, Hiroki Fujibayashi, Hiroki Matsumura, Fumiya Hori, Shunsaku Kitagawa, Kenji Ishida, Yo Tokunaga, Hironori Sakai, Shinsaku Kambe, Ai Nakamura, Yusei Shimizu, Yoshiya Homma, Dexin Li, Fuminori Honda, Dai Aoki

Superconducting (SC) state has spin and orbital degrees of freedom, and spin-triplet superconductivity shows multiple SC phases due to the presence of these degrees of freedom. However, the observation of spin-direction rotation occurring inside the SC state (SC spin rotation) has hardly been reported. UTe2, a recently discovered topological superconductor, exhibits various SC phases under pressure: SC state at ambient pressure (SC1), high-temperature SC state above 0.5 GPa (SC2), and low-temperature SC state above 0.5 GPa (SC3). We performed nuclear magnetic resonance and AC susceptibility measurements on single-crystal UTe2. The b-axis spin susceptibility remains unchanged in SC2, unlike in SC1, and decreases below the SC2-SC3 transition with spin modulation. These unique properties in SC3 arise from the coexistence of two SC order parameters. Our NMR results confirm the spin-triplet superconductivity with SC spin parallel to b in SC2, and unveil the remaining of spin degrees of freedom in superconducting UTe2.

Electronic transport and thermoelectricity in selenospinel Cu$_{6-x}$Fe$_{4+x}$Sn$_{12}$Se$_{32}$. (arXiv:2307.15797v1 [cond-mat.mtrl-sci])
Yu Liu, Zhixiang Hu, Xiao Tong, David Graf, C. Petrovic

We report a study of selenospinel Cu$_{6-x}$Fe$_{4+x}$Sn$_{12}$Se$_{32}$ ($x$ = 0, 1, 2) single crystals, which crystalize in a cubic structure with the $Fd\overline{3}m$ space group, and show typical semiconducting behavior. The large discrepancy between the activation energy for electrical conductivity $E_\rho$ (32.3 $\sim$ 69.8 meV), and for thermopower $E_\textrm{S}$ (3.2 $\sim$ 11.5 meV), indicates a polaronic transport mechanism between 350 and 50 K. With decreasing temperature, it evolves into variable-range hopping conduction. Furthermore, the heat capacity shows a hump around 25(5) K and diverges from the Debye $T^3$ law at low temperatures, indicating the observation of structural glassy features in these crystalline solids.

Comment on Hess et al. Phys. Rev. Lett. {\bf 130}, 207001 (2023). (arXiv:2307.15813v1 [cond-mat.mes-hall])
A. Antipov, W. Cole, K. Kalashnikov, F. Karimi, R. Lutchyn, C. Nayak, D. Pikulin, G. Winkler

In this comment, we show that the model introduced in Hess et al. Phys. Rev. Lett. {\bf 130}, 207001 (2023) fails the topological gap protocol (TGP) (Pikulin et al., arXiv:2103.12217 and M. Aghaee et al., Phys. Rev. B 107, 245424 (2023)). In addition, we discuss this model in the broader context of how the TGP has been benchmarked.

Epitaxial Kagome Thin Films as a Platform for Topological Flat Bands. (arXiv:2307.15828v1 [cond-mat.mtrl-sci])
Shuyu Cheng, M. Nrisimhamurty, Tong Zhou, Nuria Bagues, Wenyi Zhou, Alexander J. Bishop, Igor Lyalin, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, David W. McComb, Igor Zutic, Roland K. Kawakami

Systems with flat bands are ideal for studying strongly correlated electronic states and related phenomena. Among them, kagome-structured metals such as CoSn have been recognized as promising candidates due to the proximity between the flat bands and the Fermi level. A key next step will be to realize epitaxial kagome thin films with flat bands to enable tuning of the flat bands across the Fermi level via electrostatic gating or strain. Here we report the band structures of epitaxial CoSn thin films grown directly on insulating substrates. Flat bands are observed using synchrotron-based angle-resolved photoemission spectroscopy (ARPES). The band structure is consistent with density functional theory (DFT) calculations, and the transport properties are quantitatively explained by the band structure and semiclassical transport theory. Our work paves the way to realize flat band-induced phenomena through fine-tuning of flat bands in kagome materials.

Evidence for Two Dimensional Anisotropic Luttinger Liquids at Millikelvin Temperatures. (arXiv:2307.15881v1 [cond-mat.mes-hall])
Guo Yu, Pengjie Wang, Ayelet J. Uzan, Yanyu Jia, Michael Onyszczak, Ratnadwip Singha, Xin Gui, Tiancheng Song, Yue Tang, Kenji Watanabe, Takashi Taniguchi, Robert J. Cava, Leslie M. Schoop, Sanfeng Wu

While Landau's Fermi liquid theory provides the standard description for two- and three-dimensional (2D/3D) conductors, the physics of interacting one-dimensional (1D) conductors is governed by the distinct Luttinger liquid (LL) theory. Can a LL-like state, in which electronic excitations are fractionalized modes, emerge in a 2D system as a stable zero-temperature phase? This long-standing question, first brought up by Anderson decades ago, is crucial in the study of non-Fermi liquids but remains unsettled. A recent experiment identified a moir\'e superlattice of twisted bilayer tungsten ditelluride (tWTe_2) with a small interlayer twist angle as a 2D host of the LL physics at temperatures of a few kelvins. Here we report experimental evidence for a 2D anisotropic LL state in a substantially reduced temperature regime, down to at least 50 mK, spontaneously formed in a tWTe_2 system with a twist angle of ~ 3 degree. While the system is metallic-like and nearly isotropic above 2 K, a dramatically enhanced electronic anisotropy develops in the millikelvin regime, featuring distinct transport behaviors along two orthogonal in-plane directions. In the strongly anisotropic phase, we observe transport characteristics of a 2D LL phase, i.e., the universal power law scaling behaviors in across-wire conductance and a zero-bias dip in the differential resistance along the wire direction. Our results represent a step forward in the search for stable LL physics beyond 1D and related unconventional quantum matter.

Fano resonances in tilted Weyl semimetals in an oscillating quantum well. (arXiv:2307.15928v1 [cond-mat.mes-hall])
Souvik Das, Arnab Maity, Rajib Sarkar, Anirudha Menon, Tanay Nag, Banasri Basu

Considering low-energy model of tilted Weyl semimetal, we study the electronic transmission through a periodically driven quantum well, oriented in the transverse direction with respect to the tilt. We adopt the formalism of Floquet scattering theory and investigate the emergence of Fano resonances as an outcome of matching between the Floquet sidebands and quasi-bound states. The Fano resonance energy changes linearly with the tilt strength suggesting the fact that tilt-mediated part of quasi-bound states energies depends on the above factor. Given a value of momentum parallel (perpendicular) to the tilt, we find that the energy gap between two Fano resonances, appearing for two adjacent values of transverse (collinear) momentum with respect to the tilt direction, is insensitive (sensitive) to the change in the tilt strength. Such a coupled (decoupled) behavior of tilt strength and the collinear (transverse) momentum can be understood from the tilt-mediated and normal parts of the quasi-bound state energies inside the potential well. We vary the other tilt parameters and chirality of the Weyl points to conclusively verify exact form of the tilt-mediated part of the quasi-bound state energy that is the same as the tilt term in the static dispersion. Our work paves the way to probe the tilt-mediated part of quasi-bound state energy for understanding the complex interplay between the tilt and Fano resonance.

Unconventional optical response in monolayer graphene upon dominant intraband scattering. (arXiv:2307.15945v1 [cond-mat.mes-hall])
Palash Saha, Bala Murali Krishna Mariserla

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

Comparative $^{181}$Ta-NQR Study of Weyl Monopnictides TaAs and TaP: Relevance of Weyl Fermion Excitations. (arXiv:2307.16009v1 [cond-mat.str-el])
Tetsuro Kubo, Hiroshi Yasuoka, Balázs Dóra, Deepa Kasinathan, Yurii Prots, Helge Rosner, Takuto Fujii, Marcus Schmidt, Michael Baenitz

Based on our first detailed $^{181}$Ta nuclear quadrupole resonance (NQR) studies from 2017 on the Weyl semimetal TaP, we now extended our NQR studies to another Ta-based monopnictide TaAs. In the present work, we have determined the temperature-dependent $^{181}$Ta-NQR spectra, the spin-lattice relaxation time $T_{1}$, and the spin-spin relaxation time $T_{2}$. We found the following characteristic features that showed great contrast to what was found in TaP: (1) The quadrupole coupling constant and asymmetry parameter of EFG, extracted from three NQR frequencies, have a strong temperature dependence above $\sim$80 K that cannot be explained by the density functional theory calculation incorporating the thermal expansion of the lattice. (2) The temperature dependence of the spin-lattice relaxation rate, $1/T_{1} T$, shows a $T^{4}$ power law behavior above $\sim$30 K. This is a great contrast with the $1/T_{1} T \propto T^{2}$ behavior found in TaP, which was ascribed to the magnetic excitations at the Weyl nodes with a temperature-dependent orbital hyperfine coupling. (3) Regarding the nuclear spin-spin interaction, we found the spin-echo signal decays with the pulse separation simply by a Lorentzian function in TaAs, but we have observed spin-echo modulations in TaP that is most likely due to the indirect nuclear spin-spin coupling via virtually excited Weyl fermions. From our experimental findings, we conclude that the present NQR results do not show dominant contributions from Weyl fermion excitations in TaAs.

Swapping exchange and spin-orbit induced correlated phases in ex-so-tic van der Waals heterostructures. (arXiv:2307.16025v1 [cond-mat.mtrl-sci])
Yaroslav Zhumagulov, Denis Kochan, Jaroslav Fabian

Ex-so-tic van der Waals heterostructures take advantage of the electrically tunable layer polarization to swap proximity exchange and spin-orbit coupling in the electronically active region. Perhaps the simplest example is Bernal bilayer graphene (BBG) encapsulated by a layered magnet from one side and a strong spin-orbit material from the other. Taking WS$_2$/BBG/Cr$_2$Ge$_2$Te$_6$ as a representative ex-so-tronic device, we employ realistic \emph{ab initio}-inspired Hamiltonians and effective electron-electron interactions to investigate the emergence of correlated phases within the random phase approximation. We find that for a given doping level, exchange and spin-orbit coupling induced Stoner and intervalley coherence instabilities can be swapped, allowing to explore the full spectrum of correlated phases within a single device.

Single-spin spectroscopy of spontaneous and phase-locked spin torque oscillator dynamics. (arXiv:2307.16049v1 [cond-mat.mes-hall])
Adrian Solyom, Michael Caouette-Mansour, Brandon Ruffolo, Patrick Braganca, Lilian Childress, Jack Sankey

We employ N-$V$ magnetometry to measure the stray field dynamics of a ferromagnetic permalloy nanowire driven by spin-orbit torques. Specifically, we observe the optically detected magnetic resonance (ODMR) signatures of both spontaneous DC-driven magnetic oscillations and phase-locking to a second harmonic drive, developing a simple macrospin model that captures the salient features. We also observe signatures of dynamics beyond the macrospin model, including an additional ODMR feature (associated with a second SW mode) and one mode sapping power from another. Our results provide additional insight into N-$V$-spin wave coupling mechanisms, and represent a new modality for sub-wavelength N-$V$ scanned probe microscopy of nanoscale magnetic oscillators.

Novel Topological Anderson insulating phases in the interacting Haldane model. (arXiv:2307.16053v1 [cond-mat.str-el])
Joao S. Silva, Eduardo V. Castro, Rubem Mondaini, María A. H. Vozmediano, M. Pilar López-Sancho

We analyze the influence of disorder and strong correlations on the topology in two dimensional Chern insulators. A mean field calculation in the half-filled Haldane model with extended Hubbard interactions and Anderson disorder shows that disorder favors topology in the interacting case and extends the topological phase to a larger region of the Hubbard parameters. In the absence of a staggered potential, we find a novel disorder-driven topological phase with Chern number C=1, with co-existence of topology with long range spin and charge orders. More conventional topological Anderson insulating phases are also found in the presence of a finite staggered potential.

Easing the equilibration of spin systems with quenched disorder in Population Annealing by topological-defect-driven non-local updates. (arXiv:2307.16087v1 [cond-mat.dis-nn])
David Cirauqui, Miguel Ángel García-March, José Ramón Martínez Saavedra, Maciej Lewenstein, Przemysław R. Grzybowski

Population Annealing, the currently state-of-the-art algorithm for solving spin-glass systems, sometimes finds hard disorder instances for which its equilibration quality at each temperature step is severely damaged. In such cases one can therefore not be sure about having reached the true ground state without vastly increasing the computational resources. In this work we overcome this problem by proposing a quantum-inspired modification of Population Annealing. Here we focus on three-dimensional random plaquette gauge model which ground state energy problem seems to be much harder to solve than standard spin-glass Edwards-Anderson model. In analogy to the Toric Code, by allowing single bond flips we let the system explore non-physical states, effectively expanding the configurational space by the introduction of topological defects that are then annealed through an additional field parameter. The dynamics of these defects allow for the effective realization of non-local cluster moves, potentially easing the equilibration process. We study the performance of this new method in three-dimensional random plaquette gauge model lattices of various sizes and compare it against Population Annealing. With that we conclude that the newly introduced non-local moves are able to improve the equilibration of the lattices, in some cases being superior to a normal Population Annealing algorithm with a sixteen times higher computational resource investment.

Direct and Indirect methods of electrocaloric effect determination and energy storage calculation in (Na0.8K0.2)0.5Bi0.5TiO3 ceramic. (arXiv:2307.16232v1 [cond-mat.mtrl-sci])
Pravin Varade, Adityanarayan H. Pandey, N. Shara Sowmya, S. M. Gupta, Abhay Bhisikar, N. Venkataramani, A. R. Kulkarni

The coexistence of multiple structural phases and field induced short-range to long-range order transition in ferroelectric materials, leads to a strong electrocaloric effect (ECE) and electrical energy storage density (Wrec) in the vicinity of ferroelectric to non-ergodic phase transition in NKBT ceramic. Structural analysis using X-ray diffraction, Raman spectroscopy and TEM studies ascertained the coexistence of tetragonal (P4mm) and rhombohedral (R3c) phases. Dielectric study has revealed a critical slowing down of polar domain dynamics below a diffuse phase transition. Present investigation reports ECE in lead-free (Na0.8K0.2)0.5Bi0.5TiO3 (NKBT) ceramic by direct and indirect methods, which confirm the multifunctional nature of NKBT and its usefulness for applications in refrigeration and energy storage. A direct method of EC measurement in NKBT ceramic exhibits significant adiabatic temperature change ({\Delta}T) ~ 1.10 K and electrocaloric strength ({\xi}) ~ 0.55 Kmm/kV near the ferroelectric to non-ergodic phase transition at an external applied field of 20 kV/cm. A highest recoverable energy (Wrec) ~ 0.78 J/cm3 and electrical storage efficiency ({\eta}) ~ 86% are achieved at 423 K and an applied field of 20 kV/cm. This behavior is ascribed to the delicate balance between the field induced order-disordered transition and the thermal energy needed to disrupt field induced co-operative interaction.

Topological electronic bands in crystalline solids. (arXiv:2307.16258v1 [cond-mat.str-el])
Andrew T. Boothroyd

Topology is now securely established as a means to explore and classify electronic states in crystalline solids. This review provides a gentle but firm introduction to topological electronic band structure suitable for new researchers in the field. I begin by outlining the relevant concepts from topology, then give a summary of the theory of non-interacting electrons in periodic potentials. Next, I explain the concepts of the Berry phase and Berry curvature, and derive key formulae. The remainder of the article deals with how these ideas are applied to classify crystalline solids according to the topology of the electronic states, and the implications for observable properties. Among the topics covered are the role of symmetry in determining band degeneracies in momentum space, the Chern number and Z2 topological invariants, surface electronic states, two- and three-dimensional topological insulators, and Weyl and Dirac semimetals

Ion-beam-milled graphite nanoribbons as mesoscopic carbon-based polarizers. (arXiv:2307.16340v1 [cond-mat.mes-hall])
Marcin Muszyński, Igor Antoniazzi, Bruno Camargo

We demonstrate optical reflectivity and Raman responses of graphite microstructures as a function of light polarization when the incident light is applied perpendicular to the material's stacking direction (c-axis). For this, we employed novel graphite nanoribbons with edges polished through ion-beam etching. In this unique configuration, a strong polarization dependence of the D, G, and 2D Raman modes is observed. At the same time, polarized reflectivity measurements demonstrate the potential of such a device as a carbon-based, on-chip polarizer. We discuss the advantages of the proposed fabrication method as opposed to the mechanical polishing of bulk crystals.

Spin decoherence in VOPc@graphene nanoribbon complexes. (arXiv:2307.16403v1 [cond-mat.mes-hall])
Xiao Chen, James N. Fry, H. P. Cheng

Carbon nanoribbon or nanographene qubit arrays can facilitate quantum-to-quantum transduction between light, charge, and spin, making them an excellent testbed for fundamental science in quantum coherent systems and for the construction of higher-level qubit circuits. In this work, we study spin decoherence due to coupling with a surrounding nuclear spin bath of an electronic molecular spin of a vanadyl phthalocyanine (VOPc) molecule integrated on an armchair-edged graphene nanoribbon (GNR). Density functional theory (DFT) is used to obtain ground state atomic configurations. Decay of spin coherence in Hahn echo experiments is then simulated using the cluster correlation expansion method with a spin Hamiltonian involving hyperfine and electric field gradient tensors calculated from DFT. We find that the decoherence time $T_2$ is anisotropic with respect to magnetic field orientation and determined only by the hydrogen nuclear spins both on VOPc and GNR. Large electron spin echo envelope modulation (ESEEM) due to nitrogen and vanadium nuclear spins is present at specific field ranges and can be completely suppressed by tuning the magnetic field. The relation between these field ranges and the hyperfine interactions is analyzed. The effects of interactions with the nuclear quadrupole moments are also studied, validating the applicability and limitations of the spin Hamiltonian when they are disregarded.

Magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulators. (arXiv:2307.16435v1 [cond-mat.mes-hall])
Wan-Qing Zhu, Wen-Yu Shan

Control and detection of antiferromagnetic topological materials are challenging since the total magnetization vanishes. Here we investigate the magneto-optical Kerr and Faraday effects in bilayer antiferromagnetic insulator MnBi$_2$Te$_4$. We find that by breaking the combined mirror symmetries with either perpendicular electric field or external magnetic moment, Kerr and Faraday effects occur. Under perpendicular electric field, antiferromagnetic topological insulators (AFMTI) show sharp peaks at the interband transition threshold, whereas trivial insulators show small adjacent positive and negative peaks. Gate voltage and Fermi energy can be tuned to reveal the differences between AFMTI and trivial insulators. We find that AFMTI with large antiferromagnetic order can be proposed as a pure magneto-optical rotator due to sizable Kerr (Faraday) angles and vanishing ellipticity. Under external magnetic moment, AFMTI and trivial insulators are significantly different in the magnitude of Kerr and Faraday angles and ellipticity. For the qualitative behaviors, AFMTI shows distinct features of Kerr and Faraday angles when the spin configurations of the system change. These phenomena provide new possibilities to optically detect and manipulate the layered topological antiferromagnets.

Fourier transformation based analysis routine for intermixed longitudinal and transversal hysteretic data for the example of a magnetic topological insulator. (arXiv:2307.16450v1 [cond-mat.mes-hall])
Erik Zimmermann, Michael Schleenvoigt, Alina Rupp, Gerrit Behner, Jan Karthein, Justus Teller, Peter Schüffelgen, Hans Lüth, Detlev Grützmacher, Thomas Schäpers

We present a symmetrization routine that optimizes and eases the analysis of data featuring the anomalous Hall effect. This technique can be transferred to any hysteresis with (point-)symmetric behaviour. The implementation of the method is demonstrated exemplarily using intermixed longitudinal and transversal data obtained from a chromium-doped ternary topological insulator revealing a clear hysteresis. Furthermore, by introducing a mathematical description of the anomalous Hall hysteresis based on the error function precise values of the height and coercive field are determined.

Emergence of stable meron quartets in twisted magnets. (arXiv:2307.16505v1 [cond-mat.mes-hall])
Kyoung-Min Kim, Gyungchoon Go, Moon Jip Park, Se Kwon Kim

The investigation of twist engineering in easy-axis magnetic systems has revealed the remarkable potential for generating topological spin textures, such as magnetic skyrmions. Here, by implementing twist engineering in easy-plane magnets, we introduce a novel approach to achieve fractional topological spin textures such as merons. Through atomistic spin simulations on twisted bilayer magnets, we demonstrate the formation of a stable double meron pair in two magnetic layers, which we refer to as the "Meron Quartet" (MQ). Unlike merons in a single pair, which is unstable against pair annihilation, the merons within the MQ exhibit exceptional stability against pair annihilation due to the protective localization mechanism induced by the twist that prevents the collision of the meron cores. Furthermore, we showcase that the stability of the MQ can be enhanced by adjusting the twist angle, resulting in increased resistance to external perturbations such as external magnetic fields. Our findings highlight the twisted magnet as a promising platform for investigating the intriguing properties of merons, enabling their realization as stable magnetic quasiparticles in van der Waals magnets.

Violation of the Wiedemann-Franz law in coupled thermal and power transport of optical waveguide arrays. (arXiv:2307.16529v1 [cond-mat.mes-hall])
Meng Lian, Yin-Jie Chen, Yue Geng, Yun-Tian Chen, Jing-Tao Lü

In isolated nonlinear optical waveguide arrays with bounded energy spectrum, simultaneous conservation of energy and power of the optical modes enables study of coupled thermal and particle transport in the negative temperature regime. Here, based on exact numerical simulation and rationale from Landauer formalism, we predict generic violation of the Wiedemann-Franz law in such systems. This is rooted in the spectral decoupling of thermal and power current of optical modes, and their different temperature dependence. Our work extends the study of coupled thermal and particle transport into unprecedented regimes, not reachable in natural condensed matter and atomic gas systems.

Two-Dimensional Moir\'e Polaronic Electron Crystals. (arXiv:2307.16563v1 [cond-mat.str-el])
Eric A. Arsenault, Yiliu Li, Birui Yang, Xi Wang, Heonjoon Park, Edoardo Mosconi, Enrico Ronca, Takashi Taniguchi, Kenji Watanabe, Daniel Gamelin, Andrew Millis, Cory R. Dean, Filippo de Angelis, Xiaodong Xu, X.-Y. Zhu

Realizing quantum phases of electrons with high critical temperatures (Tc) has been one of the most important goals in quantum materials research, as exemplified by the longstanding and sometimes contentious quest for high Tc superconductors. Recently, 2D moir\'e materials have emerged as the most versatile platform for the realization of a broad range of quantum phases. These quantum phases are commonly observed at cryogenic temperatures, but a few of them exhibit sufficiently high Tc, e.g., ~ 150 K for Mott insulator states in transition metal dichalcogenide (TMD) moir\'e interfaces. Here, we explore the origins of the stability of correlated states in WSe2/WS2 moir\'e superlattices by measuring the time scales of melting and their temperature dependences. Using exciton sensing and pump-probe reflectance spectroscopy, we find that ultrafast electronic excitation leads to melting of the Mott states on a time scale of 3.3 ps (at T = 11 K), which is approximately five times longer than that predicted from the charge hopping integral between moir\'e unit cells. We further find that the melting rates are thermally activated, with activation energies of Ea = 18 meV and 13 meV for the correlated states with one and two holes (v = -1 and -2) per moir\'e unit cell, respectively, suggesting significant electron-phonon coupling. The overall temperature dependences in the exciton oscillator strength, a proxy to the order parameter for the correlated states, gives estimates of Tc in agreement with the extracted Ea. Density functional theory (DFT) calculations on the moir\'e scale confirm polaron formation in the v = -1 Mott state and predict a hole polaron binding energy of 16 meV, in agreement with experiment. These findings suggest a close interplay of electron-electron and electron-phonon interactions in the formation of polaronic Mott insulators at TMD moir\'e interfaces.

On-surface synthesis and characterization of Teranthene and Hexanthene: Ultrashort graphene nanoribbons with mixed armchair and zigzag edges. (arXiv:2307.16596v1 [cond-mat.mtrl-sci])
Gabriela Borin Barin, Marco Di Giovannantonio, Thorsten G. Lohr, Shantanu Mishra, Amogh Kinikar, Mickael L. Perrin, Jan Overbeck, Michel Calame, Xinliang Feng, Roman Fasel, Pascal Ruffieux

Graphene nanoribbons (GNRs) exhibit a broad range of physicochemical properties that critically depend on their width and edge topology. While the chemically stable GNRs with armchair edges (AGNRs) are semiconductors with width-tunable band gap, GNRs with zigzag edges (ZGNRs) host spin-polarized edge states, which renders them interesting for applications in spintronic and quantum technologies. However, these states significantly increase their reactivity. For GNRs fabricated via on-surface synthesis under ultrahigh vacuum conditions on metal substrates, the expected reactivity of zigzag edges is a serious concern in view of substrate transfer and device integration under ambient conditions, but corresponding investigations are scarce. Using 10-bromo-9,9':10',9''-teranthracene as a precursor, we have thus synthesized hexanthene (HA) and teranthene (TA) as model compounds for ultrashort GNRs with mixed armchair and zigzag edges, characterized their chemical and electronic structure by means of scanning probe methods, and studied their chemical reactivity upon air exposure by Raman spectroscopy. We present a detailed identification of molecular orbitals and vibrational modes, assign their origin to armchair or zigzag edges, and discuss the chemical reactivity of these edges based on characteristic Raman spectral features.

Reliable Synthesis of Large-Area Monolayer WS2 Single Crystals, Films, and Heterostructures with Extraordinary Photoluminescence Induced by Water Intercalation. (arXiv:2307.16629v1 [cond-mat.mtrl-sci])
Qianhui Zhang, Jianfeng Lu, Ziyu Wang, Zhigao Dai, Yupeng Zhang, Fuzhi Huang, Qiaoliang Bao, Wenhui Duan, Michael S. Fuhrer, Changxi Zheng

Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold great potential for future low-energy optoelectronics owing to their unique electronic, optical, and mechanical properties. Chemical vapor deposition (CVD) is the technique widely used for the synthesis of large-area TMDs. However, due to high sensitivity to the growth environment, reliable synthesis of monolayer TMDs via CVD remains challenging. Here we develop a controllable CVD process for large-area synthesis of monolayer WS2 crystals, films, and in-plane graphene-WS2 heterostructures by cleaning the reaction tube with hydrochloric acid, sulfuric acid and aqua regia. The concise cleaning process can remove the residual contaminates attached to the CVD reaction tube and crucibles, reducing the nucleation density but enhancing the diffusion length of WS2 species. The photoluminescence (PL) mappings of a WS2 single crystal and film reveal that the extraordinary PL around the edges of a triangular single crystal is induced by ambient water intercalation at the WS2-sapphire interface. The extraordinary PL can be controlled by the choice of substrates with different wettabilities.

Rheology of Pseudomonas fluorescens biofilms: from experiments to predictive DPD mesoscopic modelling. (arXiv:2307.16641v1 [cond-mat.soft])
Jose Mart.n-Roca, Valentino Bianco, Francisco Alarcon, Ajay K. Monnappa, Paolo Natale, Francisco Monroy, Belen Orgaz, Ivan L.pez-Montero, Chantal Valeriani

Bacterial biofilms mechanically behave as viscoelastic media consisting of micron-sized bacteria crosslinked to a selfproduced network of extracellular polymeric substances (EPS) embedded in water. Structural principles for numerical modelling aim at describing mesoscopic viscoelasticity without loosing detail on the underlying interactions existing in wide regimes of deformation under hydrodynamic stress. Here we approach the computational challenge to model bacterial biofilms for predictive mechanics in silico under variable stress conditions. Up-to-date models are not entirely satisfactory due to the plethora of parameters required to make them functioning under the effects of stress. As guided by the structural depiction gained in a previous work with Pseudomonas fluorescens (Jara et al. Front. Microbiol. (2021)), we propose a mechanical modeling by means of Dissipative Particle Dynamics (DPD), which captures the essentials of the topological and compositional interactions between bacteria particles and crosslinked EPS-embedding under imposed shear. The P. fluorescens biofilms have been modeled under mechanical stress mimicking shear stresses as undergone in vitro. The predictive capacity for mechanical features in DPD-simulated biofilms has been investigated by varying the externally imposed field of shear strain at variable amplitude and frequency. The parametric map of essential biofilm ingredients has been explored by making the rheological responses to emerge among conservative mesoscopic interactions and frictional dissipation in the underlying microscale. The proposed coarse grained DPD simulation qualitatively catches the rheology of the P. fluorescens biofilm over several decades of dynamic scaling.

Femtomolar detection of the heart failure biomarker NT-proBNP in artificial saliva using an immersible liquid-gated aptasensor with reduced graphene oxide. (arXiv:2307.16692v1 [cond-mat.mtrl-sci])
Stefan Jaric, Anastasiia Kudriavtseva, Nikita Nekrasov, Alexey V. Orlov, Ivan A. Komarov, Leonty A. Barsukov, Ivana Gadjanski, Petr I. Nikitin, Ivan Bobrinetskiy

Measuring NT-proBNP biomarker is recommended for preliminary diagnostics of the heart failure. Recent studies suggest a possibility of early screening of biomarkers in saliva for non-invasive identification of cardiac diseases at the point-of-care. However, NT-proBNP concentrations in saliva can be thousand times lower than in blood plasma, going down to pg/mL level. To reach this level, we developed a label-free aptasensor based on a liquid-gated field effect transistor using a film of reduced graphene oxide monolayer (rGO-FET) with immobilized NT-proBNP specific aptamer. We found that, depending on ionic strength of tested solutions, there were different levels of correlation in responses of electrical parameters of the rGO-FET aptasensor, namely, the Dirac point shift and transconductance change. The correlation in response to NT-proBNP was high for 1.6 mM phosphate-buffered saline (PBS) and zero for 16 mM PBS in a wide range of analyte concentrations, varied from 1 fg/mL to 10 ng/mL. The effect in transconductance and Dirac point shift in PBS solutions of different concentrations are discussed. The biosensor exhibited a high sensitivity for both transconductance (2*10E-6 S/decade) and Dirac point shift (2.3 mV/decade) in diluted PBS with the linear range from 10 fg/ml to 1 pg/ml. The aptasensor performance has been also demonstrated in undiluted artificial saliva with the achieved limit of detection down to 41 fg/mL (~4.6 fM).

Electron correlations and superconductivity in La$_3$Ni$_2$O$_7$ under pressure tuning. (arXiv:2307.16697v1 [cond-mat.supr-con])
Zhiguang Liao, Lei Chen, Guijing Duan, Yiming Wang, Changle Liu, Rong Yu, Qimiao Si

Motivated by the recent discovery of superconductivity in La$_3$Ni$_2$O$_7$ under pressure, we discuss the basic ingredients of a model that captures the evolution of pressure tuning. In particular, we study the effects of electron correlations of a bilayer Hubbard model including the Ni $3d$ $x^2-y^2$ and $z^2$ orbitals. By performing the calculation in the bonding-antibonding molecular orbital basis, we show the ground state of the model crosses over from a low-spin $S=1/2$ state to a high-spin $S=3/2$ state. In the high-spin state, the two $x^2-y^2$ and the bonding $z^2$ orbitals are all close to half-filling. It promotes an orbital-selective Mott phase where the $x^2-y^2$ orbitals are Mott localized while the $z^2$ orbitals are renormalized but remaining itinernant. Strong orbital selectivity is shown to exist in a broad crossover regime of the phase diagram. Based on these results, we construct an effective multiorbital $t$-$J$ model to describe the superconductivity of the system, and find the leading pairing channel to be an intraorbital spin singlet with a competition between the extended $s$-wave and $d_{x^2-y^2}$ symmetries. Our results highlight the role of strong multiorbital correlation effects in driving the superconductivity of La$_3$Ni$_2$O$_7$.

Stability via symmetry breaking in interacting driven systems. (arXiv:2307.16743v1 [quant-ph])
Andrew Pocklington, Aashish A. Clerk

Photonic and bosonic systems subject to incoherent, wide-bandwidth driving cannot typically reach stable finite-density phases using only non-dissipative Hamiltonian nonlinearities; one instead needs nonlinear losses, or a finite pump bandwidth. We describe here a very general mechanism for circumventing this common limit, whereby Hamiltonian interactions can cut-off heating from a Markovian pump, by effectively breaking a symmetry of the unstable, linearized dynamics. We analyze two concrete examples of this mechanism. The first is a new kind of $\mathcal{PT}$ laser, where Hermitian Hamiltonian interactions can move the dynamics between the $\mathcal{PT}$ broken and unbroken phases and thus induce stability. The second uses onsite Kerr or Hubbard type interactions to break the chiral symmetry in a topological photonic lattice, inducing exotic phenomena from topological lasing to the stabilization of Fock states in a topologically protected edge mode.

Nonlinearity-induced topological phase transition characterized by the nonlinear Chern number. (arXiv:2307.16827v1 [cond-mat.mes-hall])
Kazuki Sone, Motohiko Ezawa, Yuto Ashida, Nobuyuki Yoshioka, Takahiro Sagawa

As first demonstrated by the characterization of the quantum Hall effect by the Chern number, topology provides a guiding principle to realize robust properties of condensed matter systems immune to the existence of disorder. The bulk-boundary correspondence guarantees the emergence of gapless boundary modes in a topological system whose bulk exhibits nonzero topological invariants. Although some recent studies have suggested a possible extension of the notion of topology to nonlinear systems such as photonics and electrical circuits, the nonlinear counterpart of topological invariant has not yet been understood. Here, we propose the nonlinear extension of the Chern number based on the nonlinear eigenvalue problems in two-dimensional systems and reveal the bulk-boundary correspondence beyond the weakly nonlinear regime. Specifically, we find the nonlinearity-induced topological phase transitions, where the existence of topological edge modes depends on the amplitude of oscillatory modes. We propose and analyze a minimal model of a nonlinear Chern insulator whose exact bulk solutions are analytically obtained and indicate the amplitude dependence of the nonlinear Chern number, for which we confirm the nonlinear counterpart of the bulk-boundary correspondence in the continuum limit. Thus, our result reveals the existence of genuinely nonlinear topological phases that are adiabatically disconnected from the linear regime, showing the promise for expanding the scope of topological classification of matter towards the nonlinear regime.

Topological $n$-root Su-Schrieffer-Heeger model in a non-Hermitian photonic ring system. (arXiv:2307.16855v1 [physics.optics])
David Viedma, Anselmo M. Marques, Ricardo G. Dias, Verònica Ahufinger

Square-root topology is one of the newest additions to the ever expanding field of topological insulators (TIs). It characterizes systems that relate to their parent TI through the squaring of their Hamiltonians. Extensions to $2^n$-root topology, where $n$ is the number of squaring operations involved in retrieving the parent TI, were quick to follow. Here, we go one step further and develop the framework for designing general $n$-root TIs, with $n$ any positive integer, using the Su-Schrieffer-Heeger (SSH) model as the parent TI from which the higher-root versions are constructed. The method relies on using loops of unidirectional couplings as building blocks, such that the resulting model is non-Hermitian and embedded with a generalized chiral symmetry. Edge states are observed at the $n$ branches of the complex energy spectrum, appearing within what we designate as a ring gap, shown to be irreducible to the usual point or line gaps. We further detail on how such an $n$-root model can be realistically implemented in photonic ring systems. Near perfect unidirectional effective couplings between the main rings can be generated via mediating auxiliary rings with modulated gains and losses. These induce high imaginary gauge fields that strongly supress couplings in one direction, while enhancing them in the other. We use these photonic lattices to validate and benchmark the analytical predictions. Our results introduce a new class of high-root topological models, as well as a route for their experimental realization.

A Quantized Interband Topological Index in Two-Dimensional Systems. (arXiv:2307.16893v1 [cond-mat.mes-hall])
Tharindu Fernando, Ting Cao

We introduce a novel gauge-invariant, quantized interband index in two-dimensional (2D) multiband systems. It provides a bulk topological classification of a submanifold of parameter space (e.g., an electron valley in a Brillouin zone), and therefore overcomes difficulties in characterizing topology of submanifolds. We confirm its topological nature by numerically demonstrating a one-to-one correspondence to the valley Chern number in $k\cdot p$ models (e.g., gapped Dirac fermion model), and the first Chern number in lattice models (e.g., Haldane model). Furthermore, we derive a band-resolved topological charge and demonstrate that it can be used to investigate the nature of edge states due to band inversion in valley systems like multilayer graphene.

Room Temperature Spin to Charge Conversion in Amorphous Topological Insulating Gd-Alloyed BixSe1-x/CoFeB Bilayers. (arXiv:1911.03323v12 [cond-mat.mtrl-sci] UPDATED)
Protyush Sahu, Yifei Yang, Yihong Fan, Henri Jaffres, Jun-Yang Chen, Xavier Devaux, Yannick Fagot-Revurat, Sylvie Migot, Enzo Rongione, Sukdheep Dhillon, Tongxin Chen, Pambiang Abel Dainone, Jean-Marie George, Yuan Lu, Jian-Ping Wang

Disordered topological insulator (TI) films have gained intense interest by benefiting from both the TIs exotic transport properties and the advantage of mass production by sputtering. Here, we report on the clear evidence of spin-charge conversion (SCC) in amorphous Gd-alloyed BixSe1-x (BSG)/CoFeB bilayers fabricated by sputtering, which could be related to the amorphous TI surface states. Two methods have been employed to study SCC in BSG/CoFeB(5 nm) bilayers with different BSG thicknesses. Firstly, spin pumping is used to generate a spin current in CoFeB and to detect SCC by inverse Edelstein effect. The maximum SCC efficiency (SCE) is measured as large as 0.035 nm in a 6 nm thick BSG sample, which shows a strong decay when tBSG increases due to the increase of BSG surface roughness. The second method is the THz time-domain spectroscopy, which reveals a small tBSG dependence of SCE, validating the occurrence of a pure interface state related SCC. Furthermore, our angle-resolved photoemission spectroscopy data show dispersive two-dimensional surface states that cross the bulk gap until to the Fermi level, strengthening the possibility of SCC due to the amorphous TI states. Our studies provide a new experimental direction towards the search for topological systems in the amorphous solids.

Reduction of the Twisted Bilayer Graphene Chiral Hamiltonian into a $2\times2$ matrix operator and physical origin of flat-bands at magic angles. (arXiv:2102.09473v4 [cond-mat.mes-hall] UPDATED)
Gerardo G. Naumis, Leonardo A. Navarro-Labastida, Enrique Aguilar-Méndez, Abdiel Espinosa-Champo

The chiral Hamiltonian for twisted graphene bilayers is written as a $2\times2$ matrix operator by a renormalization of the Hamiltonian that takes into account the particle-hole symmetry. This results in an effective Hamiltonian with an average field plus and effective non-Abelian gauge potential. The action of the proposed renormalization maps the zero-mode region into the ground state. Modes near zero energy have an antibonding nature in a triangular lattice. This leads to a phase-frustration effect associated with massive degeneration, and makes flat-bands modes similar to confined modes observed in other bipartite lattices. Suprisingly, the proposed Hamiltonian renormalization suggests that flat-bands at magic angles are akin to floppy-mode bands in flexible crystals or glasses, making an unexpected connection between rigidity topological theory and magic angle twisted two-dimensional heterostructures physics.

Enhancing Detection of Topological Order by Local Error Correction. (arXiv:2209.12428v2 [quant-ph] UPDATED)
Iris Cong, Nishad Maskara, Minh C. Tran, Hannes Pichler, Giulia Semeghini, Susanne F. Yelin, Soonwon Choi, Mikhail D. Lukin

The exploration of topologically-ordered states of matter is a long-standing goal at the interface of several subfields of the physical sciences. Such states feature intriguing physical properties such as long-range entanglement, emergent gauge fields and non-local correlations, and can aid in realization of scalable fault-tolerant quantum computation. However, these same features also make creation, detection, and characterization of topologically-ordered states particularly challenging. Motivated by recent experimental demonstrations, we introduce a new paradigm for quantifying topological states -- locally error-corrected decoration (LED) -- by combining methods of error correction with ideas of renormalization-group flow. Our approach allows for efficient and robust identification of topological order, and is applicable in the presence of incoherent noise sources, making it particularly suitable for realistic experiments. We demonstrate the power of LED using numerical simulations of the toric code under a variety of perturbations. We subsequently apply it to an experimental realization, providing new insights into a quantum spin liquid created on a Rydberg-atom simulator. Finally, we extend LED to generic topological phases, including those with non-abelian order.

Spin-statistics relation for quantum Hall states. (arXiv:2211.07788v2 [cond-mat.mes-hall] UPDATED)
Alberto Nardin, Eddy Ardonne, Leonardo Mazza

We prove a generic spin-statistics relation for the fractional quasiparticles that appear in abelian quantum Hall states on the disk. The proof is based on an efficient way for computing the Berry phase acquired by a generic quasiparticle translated in the plane along a circular path, and on the crucial fact that once the gauge-invariant generator of rotations is projected onto a Landau level, it fractionalizes among the quasiparticles and the edge. Using these results we define a measurable quasiparticle fractional spin that satisfies the spin-statistics relation. As an application, we predict the value of the spin of the composite-fermion quasielectron proposed by Jain; our numerical simulations agree with that value. We also show that Laughlin's quasielectrons satisfy the spin-statistics relation, but carry the wrong spin to be the anti-anyons of Laughlin's quasiholes. We continue by highlighting the fact that the statistical angle between two quasiparticles can be obtained by measuring the angular momentum whilst merging the two quasiparticles. Finally, we show that our arguments carry over to the non-abelian case by discussing explicitly the Moore-Read wavefunction.

Anisotropic Topological Anderson Transitions in Chiral Symmetry Classes. (arXiv:2211.09999v2 [cond-mat.dis-nn] UPDATED)
Zhenyu Xiao, Kohei Kawabata, Xunlong Luo, Tomi Ohtsuki, Ryuichi Shindou

We study quantum phase transitions of three-dimensional disordered systems in the chiral classes (AIII and BDI) with and without weak topological indices. We show that the systems with a nontrivial weak topological index universally exhibit an emergent thermodynamic phase where wave functions are delocalized along one spatial direction but exponentially localized in the other two spatial directions, which we call the quasi-localized phase. Our extensive numerical study clarifies that the critical exponent of the Anderson transition between the metallic and quasi-localized phases, as well as that between the quasi-localized and localized phases, are different from that with no weak topological index, signaling the new universality classes induced by topology. The quasi-localized phase and concomitant topological Anderson transition manifest themselves in the anisotropic transport phenomena of disordered weak topological insulators and nodal-line semimetals, which exhibit the metallic behavior in one direction but the insulating behavior in the other directions.

Mesoscopic modeling and experimental validation of thermal and mechanical properties of polypropylene nanocomposites reinforced by graphene-based fillers. (arXiv:2211.13148v2 [cond-mat.mtrl-sci] UPDATED)
Atta Muhammad, Rajat Srivastava, Nikos Koutroumanis, Dionisis Semitekolos, Eliodoro Chiavazzo, Panagiotis-Nektarios Pappas, Costas Galiotis, Pietro Asinari, Costas A. Charitidis, Matteo Fasano

The development of nanocomposites relies on structure-property relations, which necessitate multiscale modeling approaches. This study presents a modelling framework that exploits mesoscopic models to predict the thermal and mechanical properties of nanocomposites starting from their molecular structure. In detail, mesoscopic models of polypropylene (PP) and graphene based nanofillers (Graphene (Gr), Graphene Oxide (GO), and reduced Graphene Oxide (rGO)) are considered. The newly developed mesoscopic model for the PP/Gr nanocomposite provides mechanistic information on the thermal and mechanical properties at the filler-matrix interface, which can be then exploited to enhance the prediction accuracy of traditional continuum simulations by calibrating the thermal and mechanical properties of the filler-matrix interface. Once validated through a dedicated experimental campaign, this multiscale model demonstrates that with the modest addition of nanofillers (up to 2 wt.%), the Young's modulus and thermal conductivity show up to 35% and 25% enhancement, respectively, while the Poisson's ratio slightly decreases. Among the different combinations tested, PP/Gr nanocomposite shows the best mechanical properties, whereas PP/rGO demonstrates the best thermal conductivity. This validated mesoscopic model can contribute to the development of smart materials with enhanced mechanical and thermal properties based on polypropylene, especially for mechanical, energy storage, and sensing applications.

Finite-size Topology. (arXiv:2212.11300v2 [cond-mat.mes-hall] UPDATED)
Ashley M. Cook, Anne E. B. Nielsen

We show that topological characterization and classification in $D$-dimensional systems, which are thermodynamically large in only $D-\delta$ dimensions and finite in size in $\delta$ dimensions, is fundamentally different from that of systems thermodynamically large in all $D$-dimensions: as $(D-\delta)$-dimensional topological boundary states permeate into a system's $D$ dimensional bulk with decreasing system size, they hybridize to create novel topological phases characterized by a set of $\delta+1$ topological invariants, ranging from the $D$-dimensional topological invariant to the $(D-\delta)$-dimensional topological invariant. The system exhibits topological response signatures and bulk-boundary correspondences governed by combinations of these topological invariants taking non-trivial values, with lower-dimensional topological invariants characterizing fragmentation of the underlying topological phase of the system thermodynamically large in all $D$-dimensions. We demonstrate this physics for the paradigmatic Chern insulator phase, but show its requirements for realization are satisfied by a much broader set of topological systems.

Luxuriant correlation landscape in lacunar spinels: multiconfiguration expansions in molecular-orbital basis vs resonant valence structures. (arXiv:2301.03392v2 [cond-mat.str-el] UPDATED)
Thorben Petersen, Pritam Bhattacharyya, Ulrich K. Rößler, Liviu Hozoi

The valence structure of magnetic centers is one of the factors that determines the characteristics of a magnet. It may pertain to orbital degeneracy, as for $j_\text{eff}=1/2$ Kitaev magnets, or near-degeneracy, e.g. $3d$-$4s$, in cuprate superconductors. Here we explore the inner structure of magnetic moments in group-5 lacunar spinels, fascinating materials featuring multisite magnetic units in the form of tetrahedral tetramers. Our analysis reveals a very colorful landscape, much richer than the generic (...)$t_2^1$ single-configuration description applied so far to all group-5 Ga$M_4X_8$ chalcogenides, and clarifies the basic multiorbital correlations on $M_4$ units: while for V ions strong correlations yield a wave-function that can be well described in terms of four V$^{4+}$V$^{3+}$V$^{3+}$V$^{3+}$ resonant valence structures, for Nb and Ta a picture of dressed molecular-orbital-like $j_\text{eff}=3/2$ entities is more appropriate. These internal degrees of freedom likely shape vibronic couplings, phase transitions, and magneto-electric properties in each of these systems.

Mixed-State Entanglement Measures in Topological Order. (arXiv:2301.08207v2 [cond-mat.str-el] UPDATED)
Chao Yin, Shang Liu

Quantum entanglement is a particularly useful characterization of topological orders which lack conventional order parameters. In this work, we study the entanglement in topologically ordered states between two arbitrary spatial regions, using two distinct mixed-state entanglement measures: the so-called "computable cross-norm or realignment" (CCNR) negativity, and the more well-known partial-transpose (PT) negativity. We first generally compute the entanglement measures: We obtain general expressions both in (2+1)D Chern-Simons field theories under certain simplifying conditions, and in the Pauli stabilizer formalism that applies to lattice models in all dimensions. While the field-theoretic results are expected to be topological and universal, the lattice results contain nontopological/nonuniversal terms as well. This raises the important problem of continuum-lattice comparison which is crucial for practical applications. When the two spatial regions and the remaining subsystem do not have triple intersection, we solve the problem by proposing a general strategy for extracting the topological and universal terms in both entanglement measures. Examples in the (2+1)D $Z_2$ toric code model are also presented. In the presence of trisection points, however, our result suggests that the subleading piece in the PT negativity is not topological and depends on the local geometry of the trisections, which is in harmonics with a technical subtlety in the field-theoretic calculation.

Non-Abelian generalization of non-Hermitian quasicrystal: PT-symmetry breaking, localization, entanglement and topological transitions. (arXiv:2302.05710v2 [quant-ph] UPDATED)
Longwen Zhou

Non-Hermitian quasicrystal forms a unique class of matter with symmetry-breaking, localization and topological transitions induced by gain and loss or nonreciprocal effects. In this work, we introduce a non-Abelian generalization of the non-Hermitian quasicrystal, in which the interplay between non-Hermitian effects and non-Abelian quasiperiodic potentials create mobility edges and rich transitions among extended, critical and localized phases. These generic features are demonstrated by investigating three non-Abelian variants of the non-Hermitian Aubry-Andr\'e-Harper model. A unified characterization is given to their spectrum, localization, entanglement and topological properties. Our findings thus add new members to the family of non-Hermitian quasicrystal and uncover unique physics that can be triggered by non-Abelian effects in non-Hermitian systems.

Quantum $z=2$ Lifshitz criticality in one-dimensional interacting fermions. (arXiv:2302.13243v2 [cond-mat.str-el] UPDATED)
Ke Wang

We consider Lifshitz criticality (LC) with the dynamical critical exponent $z=2$ in one-dimensional interacting fermions with a filled Dirac Sea. We report that interactions have crucial effects on Lifshitz criticality. Single particle excitations are destabilized by interaction and decay into the particle-hole continuum, which is reflected in the logarithmic divergence in the imaginary part of one-loop self-energy. We show that the system is sensitive to the sign of interaction. Random-phase approximation (RPA) shows that the collective particle-hole excitations emerge only when the interaction is repulsive. The dispersion of collective modes is gapless and linear.

If the interaction is attractive, the one-loop renormalization group (RG) shows that there may exist a stable RG fixed point described by two coupling constants. We also show that the on-site interaction (without any other perturbations at the UV scale) would always turn on the relevant velocity perturbation to the quadratic Lagrangian in the RG flow, driving the system flow to the conformal-invariant criticality. In the numerical simulations of the lattice model at the half-filling, we find that, for either on-site positive or negative interactions, the dynamical critical exponent becomes $z=1$ in the infrared (IR) limit and the entanglement entropy is a logarithmic function of the system size $L$. The work paves the way to study one-dimensional interacting LCs.

Inducing superconductivity in bilayer graphene by alleviation of the Stoner blockade. (arXiv:2303.04176v2 [cond-mat.supr-con] UPDATED)
Gal Shavit, Yuval Oreg

External magnetic fields conventionally suppress superconductivity, both by orbital and paramagnetic effects. A recent experiment has shown that in a Bernal stacked bilayer graphene system, the opposite occurs -- a finite critical magnetic field is necessary to observe superconducting features occurring in the vicinity of a magnetic phase transition. We propose an extraordinary electronic-correlation-driven mechanism by which this anomalous superconductivity manifests. Specifically, the electrons tend to avoid band occupations near high density of states regions due to their mutual repulsion. Considering the nature of spontaneous symmetry breaking involved, we dub this avoidance Stoner blockade. We show how a magnetic field softens this blockade, allowing weak superconductivity to take place, consistent with experimental findings. Our principle prediction is that a small reduction of the Coulomb repulsion would result in sizable superconductivity gains, both in achieving higher critical temperatures and expanding the superconducting regime. Within the theory we present, magnetic field and spin-orbit coupling of the Ising type have a similar effect on the Bernal stacked bilayer graphene system, elucidating the emergence of superconductivity when the system is proximitized to a $\rm WSe_2$ substrate. We further demonstrate in this paper the sensitivity of superconductivity to disorder in the proposed scenario. We find that a disorder that does not violate Anderson's theorem may still induce a reduction of $T_c$ through its effect on the density of states, establishing the delicate nature of the Bernal bilayer graphene superconductor.

Floquet topological superconductors with many Majorana edge modes: topological invariants, entanglement spectrum and bulk-edge correspondence. (arXiv:2303.04674v2 [cond-mat.mes-hall] UPDATED)
Hailing Wu, Shenlin Wu, Longwen Zhou

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

Factorization of density matrices in the critical RSOS models. (arXiv:2303.15252v2 [cond-mat.stat-mech] UPDATED)
Daniel Westerfeld, Maxime Großpietsch, Hannes Kakuschke, Holger Frahm

We study reduced density matrices of the integrable critical RSOS model in a particular topological sector containing the ground state. Similar as in the spin-$1/2$ Heisenberg model it has been observed that correlation functions of this model on short segments can be `factorized': they are completely determined by a single nearest-neighbour two-point function $\omega$ and a set of structure functions. While $\omega$ captures the dependence on the system size and the state of the system the structure functions can be expressed in terms of the possible operators on the segment, in the present case representations of the Temperley-Lieb algebra $\text{TL}_n$, and are independent of the model parameters. We present explicit results for the function $\omega$ in the infinite system ground state of the model and compute multi-point local height probabilities for up to four adjacent sites for the RSOS model and the related three-point correlation functions of non-Abelian $su(2)_k$ anyons.

PiNNwall: heterogeneous electrode models from integrating machine learning and atomistic simulation. (arXiv:2303.15307v3 [cond-mat.mtrl-sci] UPDATED)
Thomas Dufils, Lisanne Knijff, Yunqi Shao, Chao Zhang

Electrochemical energy storage always involves the capacitive process. The prevailing electrode model used in the molecular simulation of polarizable electrode-electrolyte systems is the Siepmann-Sprik model developed for perfect metal electrodes. This model has been recently extended to study the metallicity in the electrode by including the Thomas-Fermi screening length. Nevertheless, a further extension to heterogeneous electrode models requires introducing chemical specificity which does not have any analytical recipes. Here, we address this challenge by integrating the atomistic machine learning code (PiNN) for generating the base charge and response kernel and the classical molecular dynamics code (MetalWalls) dedicated to the modelling of electrochemical systems, and this leads to the development of the PiNNwall interface. Apart from the cases of chemically doped graphene and graphene oxide electrodes as shown in this study, the PiNNwall interface also allows us to probe polarized oxide surfaces in which both the proton charge and the electronic charge can coexist. Therefore, this work opens the door for modelling heterogeneous and complex electrode materials often found in energy storage systems.

In-plane flexoelectricity in two-dimensional $D_{3d}$ crystals. (arXiv:2303.18124v2 [cond-mat.mtrl-sci] UPDATED)
Matteo Springolo, Miquel Royo, Massimiliano Stengel

We predict a large in-plane polarization response to bending in a broad class of trigonal two-dimensional crystals. We define and compute the relevant flexoelectric coefficients from first principles as linear-response properties of the undistorted layer, by using the primitive crystal cell. The ensuing response (evaluated for SnS$_{2}$, silicene, phosphorene and RhI$_{3}$ monolayers and for a hexagonal BN bilayer) is up to one order of magnitude larger than the out-of-plane components in the same material. We illustrate the topological implications of our findings by calculating the polarization textures that are associated with a variety of rippled and bent structures. We also determine the longitudinal electric fields induced by a flexural phonon at leading order in amplitude and momentum.

Non-Hermitian Floquet Topological Matter -- A Review. (arXiv:2305.16153v3 [quant-ph] UPDATED)
Longwen Zhou, Da-Jian Zhang

The past few years have witnessed a surge of interest in non-Hermitian Floquet topological matters due to their exotic properties resulting from the interplay between driving fields and non-Hermiticity. The present review sums up our studies on non-Hermitian Floquet topological matters in one and two spatial dimensions. We first give a bird's-eye view of the literature for clarifying the physical significance of non-Hermitian Floquet systems. We then introduce, in a pedagogical manner, a number of useful tools tailored for the study of non-Hermitian Floquet systems and their topological properties. With the aid of these tools, we present typical examples of non-Hermitian Floquet topological insulators, superconductors, and quasicrystals, with a focus on their topological invariants, bulk-edge correspondences, non-Hermitian skin effects, dynamical properties, and localization transitions. We conclude this review by summarizing our main findings and presenting our vision of future directions.

Active surface flows accelerate the coarsening of lipid membrane domains. (arXiv:2306.00218v3 [cond-mat.soft] UPDATED)
Daniel P. Arnold, Aakanksha Gubbala, Sho C. Takatori

Phase separation of multicomponent lipid membranes is characterized by the nucleation and coarsening of circular membrane domains that grow slowly in time as $\sim t^{1/3}$, following classical theories of coalescence and Ostwald ripening. In this work, we study the coarsening kinetics of phase-separating lipid membranes subjected to nonequilibrium forces and flows transmitted by motor-driven gliding actin filaments. We experimentally observe that the activity-induced surface flows trigger rapid coarsening of non-circular membrane domains that grow as $\sim t^{2/3}$, a 2$\times$ acceleration in the growth exponent compared to passive coalescence and Ostwald ripening. We analyze these results by developing analytical theories based on the Smoluchowski coagulation model and the phase field model to predict the domain growth in the presence of active flows. Our work demonstrates that active matter forces may be used to control the growth and morphology of membrane domains driven out of equilibrium.

Nonlinear Topological Mechanics in Elliptically Geared Isostatic Metamaterials. (arXiv:2307.00031v2 [cond-mat.mtrl-sci] UPDATED)
Fangyuan Ma, Zheng Tang, Xiaotian Shi, Ying Wu, Jinkyu Yang, Di Zhou, Yugui Yao, Feng Li

Despite the extensive studies of topological systems, the experimental characterizations of strongly nonlinear topological phases have been lagging. To address this shortcoming, we design and build elliptically geared isostatic metamaterials. Their nonlinear topological transitions can be realized by collective soliton motions, which stem from the transition of nonlinear Berry phase. Endowed by the intrinsic nonlinear topological mechanics, surface polar elasticity and dislocation-bound zero modes can be created or annihilated as the topological polarization reverses orientation. Our approach integrates topological physics with strongly nonlinear mechanics and promises multi-phase structures at the micro and macro scales.

Extended superconducting fluctuation region and 6e and 4e flux-quantization in a Kagome compound with a normal state of 3Q-order. (arXiv:2307.00448v2 [cond-mat.supr-con] UPDATED)
Chandra M. Varma, Ziqiang Wang

The superconducting state with the usual 2e-flux quantization formed from a normal state with 3Q charge density or loop-current order is a linear combination of 3 different paired states with an overall gauge invariant phase and two internal phases such that the phases in equilibrium are at $2\pi/3$ with respect to each other. In the fluctuation regime of such a 3-component superconductor, internal phase fluctuations are of the same class as for frustrated classical xy-spins on a triangular lattice. The fluctuation region is known therefore to be abnormally extended below the mean-field or the Kosterlitz-Thouless transition temperature. A 6e-flux and a 4e-flux quantized states can be constructed which are also eigenstates of the BCS Hamiltonian and stationary points of the Ginzburg-Landau free-energy with a transition temperature above that of the renormalized 2e-flux quantized state. Such states have no internal phases and so no frustrating internal phase fluctuations. These state however cannot acquire long-range order because their free-energy is higher than the co-existing fluctuating state of 2e flux-quantization. 6e- as well as 4e- flux-quantized Little-Parks oscillations however occur in which the resistivity increases periodically with field above that of the 2e-fluctuating state in its extended fluctuation regime, as are observed, followed at low temperatures to a condensation of the time-reversal odd 2e-quantized state

Superconductor Pb$_{10-x}$Cu$_x$(PO$_4$)$_{6O}$ showing levitation at room temperature and atmospheric pressure and mechanism. (arXiv:2307.12037v2 [cond-mat.supr-con] UPDATED)
Sukbae Lee, Jihoon Kim, Hyun-Tak Kim, Sungyeon Im, SooMin An, Keun Ho Auh

A material called LK-99, a modified-lead apatite crystal structure with the composition Pb$_{10-x}$Cu$_x$(PO$_4$)$_{6O}$ ($0.9<x<1.1$), has been synthesized using the solid-state method. The material exhibits the Ohmic metal characteristic of Pb(6s1) above its superconducting critical temperature, $T_c$, and the levitation phenomenon as Meissner effect of a superconductor at room temperature and atmospheric pressure below $T_c$. A LK-99 sample shows $T_c$ above 126.85$^\circ$C (400 K). We analyze that the possibility of room-temperature superconductivity in this material is attributed to two factors: the first being the volume contraction resulting from an insulator-metal transition achieved by substituting Pb with Cu, and the second being on-site repulsive Coulomb interaction enhanced by the structural deformation in the one-dimensional(D) chain (Pb2-O$_{1/2}$-Pb2 along the c-axis) structure owing to superconducting condensation at $T_c$. The mechanism of the room-temperature $T_c$ is discussed by 1-D BR-BCS theory.

Quantum Duality in Electromagnetism and the Fine-Structure Constant. (arXiv:2307.12927v2 [hep-th] UPDATED)
Clay Cordova, Kantaro Ohmori

We describe the interplay between electric-magnetic duality and higher symmetry in Maxwell theory. When the fine-structure constant is rational, the theory admits non-invertible symmetries which can be realized as composites of electric-magnetic duality and gauging a discrete subgroup of the one-form global symmetry. These non-invertible symmetries are approximate quantum invariances of the natural world which emerge in the infrared below the mass scale of charged particles. We construct these symmetries explicitly as topological defects and illustrate their action on local and extended operators. We also describe their action on boundary conditions and illustrate some consequences of the symmetry for Hilbert spaces of the theory defined in finite volume.

Views on gravity from condensed matter physics. (arXiv:2307.14370v2 [cond-mat.other] UPDATED)
G.E. Volovik

In the paper "Life, the Universe, and everything--42 fundamental questions", Roland Allen and Suzy Lidstr\"om presented personal selection of the fundamental questions. Here, based on the condensed matter experience, we suggest the answers to some questions concerning the vacuum energy, black hole entropy and the origin of gravity. In condensed matter we know both the many-body phenomena emerging on the macroscopic level and the microscopic (atomic) physics, which generates this emergence. It appears that the same macroscopic phenomenon may be generated by essentially different microscopic backgrounds. This points to various possible directions in study of the deep quantum vacuum of our Universe.

Learnability transitions in monitored quantum dynamics via eavesdropper's classical shadows. (arXiv:2307.15011v2 [quant-ph] UPDATED)
Matteo Ippoliti, Vedika Khemani

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.

Characterisation of the Set of Ground States of Uniformly Chaotic Finite-Range Lattice Models. (arXiv:2302.07326v2 [math-ph] CROSS LISTED)
Léo Gayral, Mathieu Sablik, Siamak Taati

Chaotic dependence on temperature refers to the phenomenon of divergence of Gibbs measures as the temperature approaches a certain value. Models with chaotic behaviour near zero temperature have multiple ground states, none of which are stable. We study the class of uniformly chaotic models, that is, those in which, as the temperature goes to zero, every choice of Gibbs measures accumulates on the entire set of ground states. We characterise the possible sets of ground states of uniformly chaotic finite-range models up to computable homeomorphisms.

Namely, we show that the set of ground states of every model with finite-range and rational-valued interactions is topologically closed and connected, and belongs to the class $\Pi_2$ of the arithmetical hierarchy. Conversely, every $\Pi_2$-computable, topologically closed and connected set of probability measures can be encoded (via a computable homeomorphism) as the set of ground states of a uniformly chaotic two-dimensional model with finite-range rational-valued interactions.

Found 10 papers in prb
Date of feed: Tue, 01 Aug 2023 03:17:06 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]+)

Photoaccelerated hot carrier transfer at ${\mathrm{MoS}}_{2}/{\mathrm{WS}}_{2}$: A first-principles study
Zhi-Guo Tao, Guo-Jun Zhu, Weibin Chu, Xin-Gao Gong, and Ji-Hui Yang
Author(s): Zhi-Guo Tao, Guo-Jun Zhu, Weibin Chu, Xin-Gao Gong, and Ji-Hui Yang

Charge transfer in type-II heterostructures plays important roles in determining device performance for photovoltaic and photocatalytic applications. However, current theoretical studies of charge transfer process do not consider the effects of operating conditions such as illuminations and yield sy…

[Phys. Rev. B 108, 014312] Published Mon Jul 31, 2023

Discrete time crystal made of topological edge magnons
Dhiman Bhowmick, Hao Sun, Bo Yang, and Pinaki Sengupta
Author(s): Dhiman Bhowmick, Hao Sun, Bo Yang, and Pinaki Sengupta

We report the emergence of time-crystalline behavior in the $π$-Berry phase protected edge states of a Heisenberg ferromagnet in the presence of an external driving field. The magnon amplification due to the external field spontaneously breaks the discrete time-translational symmetry, resulting in a…

[Phys. Rev. B 108, 014434] Published Mon Jul 31, 2023

Contrasting magnetic and magnetoelectric properties of $\mathrm{Lu}M\mathrm{W}{\mathrm{O}}_{6}\phantom{\rule{4pt}{0ex}}(M=\mathrm{Fe}$ and Cr): Role of spin frustration and noncollinear magnetic structure
Swarnamayee Mishra, Premakumar Yanda, Fabio Orlandi, Pascal Manuel, Hyun-Joo Koo, Myung-Hwan Whangbo, and A. Sundaresan
Author(s): Swarnamayee Mishra, Premakumar Yanda, Fabio Orlandi, Pascal Manuel, Hyun-Joo Koo, Myung-Hwan Whangbo, and A. Sundaresan

We report the magnetic and magnetoelectric properties of two isostructural polar compounds $\mathrm{Lu}M\mathrm{W}{\mathrm{O}}_{6}\phantom{\rule{4pt}{0ex}}(M=\mathrm{Fe}$ and Cr) that were synthesized at high pressure and high temperatures. Both compounds have a polar orthorhombic aeschynite-type st…

[Phys. Rev. B 108, 014435] Published Mon Jul 31, 2023

Disorder-induced excitation continuum in a spin-$\frac{1}{2}$ cobaltate on a triangular lattice
Bin Gao, Tong Chen, Chien-Lung Huang, Yiming Qiu, Guangyong Xu, Jesse Liebman, Lebing Chen, Matthew B. Stone, Erxi Feng, Huibo Cao, Xiaoping Wang, Xianghan Xu, Sang-Wook Cheong, Stephen M. Winter, and Pengcheng Dai
Author(s): Bin Gao, Tong Chen, Chien-Lung Huang, Yiming Qiu, Guangyong Xu, Jesse Liebman, Lebing Chen, Matthew B. Stone, Erxi Feng, Huibo Cao, Xiaoping Wang, Xianghan Xu, Sang-Wook Cheong, Stephen M. Winter, and Pengcheng Dai

A spin-1/2 triangular-lattice antiferromagnet is a prototypical frustrated quantum magnet, which exhibits remarkable quantum many-body effects that arise from the synergy between geometric spin frustration and quantum fluctuations. It can host quantum frustrated magnetic topological phenomena such a…

[Phys. Rev. B 108, 024431] Published Mon Jul 31, 2023

Density of states of tight-binding models in the hyperbolic plane
Rémy Mosseri and Julien Vidal
Author(s): Rémy Mosseri and Julien Vidal

We study the energy spectrum of tight-binding Hamiltonians for regular hyperbolic tilings. More specifically, we compute the density of states using the continued-fraction expansion of the Green's function on finite-size systems with more than ${10}^{9}$ sites and open boundary conditions. The coeff…

[Phys. Rev. B 108, 035154] Published Mon Jul 31, 2023

Conductance asymmetry in proximitized magnetic topological insulator junctions with Majorana modes
Daniele Di Miceli, Eduárd Zsurka, Julian Legendre, Kristof Moors, Thomas L. Schmidt, and Llorenç Serra
Author(s): Daniele Di Miceli, Eduárd Zsurka, Julian Legendre, Kristof Moors, Thomas L. Schmidt, and Llorenç Serra

We theoretically discuss electronic transport via Majorana states in magnetic topological insulator-superconductor junctions with an asymmetric split of the applied bias voltage. We study normal-superconductor-normal (NSN) junctions made of narrow (wirelike) or wide (filmlike) magnetic topological i…

[Phys. Rev. B 108, 035424] Published Mon Jul 31, 2023

Exciton spectrum in atomically thin monolayers: The role of hBN encapsulation
Artur O. Slobodeniuk and Maciej R. Molas
Author(s): Artur O. Slobodeniuk and Maciej R. Molas

The high-quality structures containing semiconducting transition-metal dichalcogenide (S-TMD) monolayers (MLs) required for optical and electrical studies are achieved by their encapsulation in hexagonal BN (hBN) flakes. To examine the effect of hBN thickness in these systems, we consider a model wi…

[Phys. Rev. B 108, 035427] Published Mon Jul 31, 2023

Chiral topological metals with multiple types of quasiparticle fermions and large spin Hall effect in the SrGePt family materials
Yi Shen, Yahui Jin, Yongheng Ge, Mingxing Chen, and Ziming Zhu
Author(s): Yi Shen, Yahui Jin, Yongheng Ge, Mingxing Chen, and Ziming Zhu

We present a prediction of chiral topological metals with several classes of unconventional quasiparticle fermions in a family of SrGePt-type materials in terms of first-principles calculations. In these materials, fourfold spin-3/2 Rarita-Schwinger-Weyl (RSW) fermion, sixfold excitation, and Weyl f…

[Phys. Rev. B 108, 035428] Published Mon Jul 31, 2023

Interplay between lattice gauge theory and subsystem codes
Yoshihito Kuno and Ikuo Ichinose
Author(s): Yoshihito Kuno and Ikuo Ichinose

It is now widely recognized that the toric code is a pure gauge-theory model governed by a projective Hamiltonian with topological orders. In this paper, we extend the interplay between quantum information system and gauge-theory model from the viewpoint of subsystem code, which is suitable for gaug…

[Phys. Rev. B 108, 045150] Published Mon Jul 31, 2023

Moiré superlattice and two-dimensional free-electron-like states of indium triple-layer structure on Si(111)
Shinichiro Hatta, Kenta Kuroishi, Keisuke Yukawa, Tomoka Murata, Hiroshi Okuyama, and Tetsuya Aruga
Author(s): Shinichiro Hatta, Kenta Kuroishi, Keisuke Yukawa, Tomoka Murata, Hiroshi Okuyama, and Tetsuya Aruga

We studied the growth of an indium triple-atomic-layer film and the two-dimensional free-electron-like electronic states on Si(111) by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and angle-resolved photoelectron spectroscopy (ARPES). By depositing In on the In/Si(111…

[Phys. Rev. B 108, 045427] Published Mon Jul 31, 2023

Found 2 papers in pr_res
Date of feed: Tue, 01 Aug 2023 03:17:06 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]+)

Bosonic Gaussian channel and Gaussian witness entanglement criterion of continuous variables
Xiao-yu Chen, Maoke Miao, Rui Yin, and Jiantao Yuan
Author(s): Xiao-yu Chen, Maoke Miao, Rui Yin, and Jiantao Yuan

We use quantum entanglement witnesses derived from Gaussian operators to study the separable criteria of continuous variable states. For bipartite system, we transform the validity of a Gaussian witness to a bosonic Gaussian channel problem. It follows that the maximal means of two-mode and some fou…

[Phys. Rev. Research 5, 033066] Published Mon Jul 31, 2023

Optimal and nearly optimal simulation of multiperiodic time-dependent Hamiltonians
Kaoru Mizuta
Author(s): Kaoru Mizuta

Simulating Hamiltonian dynamics is one of the most fundamental and significant tasks for characterizing quantum materials. Recently, a series of quantum algorithms employing block encoding of Hamiltonians have succeeded in providing efficient simulation of time-evolution operators on quantum compute…

[Phys. Rev. Research 5, 033067] Published Mon Jul 31, 2023

Found 1 papers in comm-phys

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

Topological magnon-photon interaction for cavity magnonics
Hyun-Woo Lee

Communications Physics, Published online: 31 July 2023; doi:10.1038/s42005-023-01316-8

Reaching the strong coupling regime in cavity magnonics is impaired by quantum decoherence effects introduced by a large size of magnet required. By mediating it via a topological insulator, the authors propose an indirect coupling mechanism to enhance the magnon-photon interaction strength.