Found 42 papers in cond-mat
Date of feed: Fri, 15 Dec 2023 01:30:00 GMT

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Defect-sensitive High-frequency Modes in a Three-Dimensional Artificial Magnetic Crystal. (arXiv:2312.08415v1 [cond-mat.mes-hall])
Rajgowrav Cheenikundil, Massimiliano d'Aquino, Riccardo Hertel

Modern three-dimensional nanofabrication methods make it possible to generate arbitrarily shaped nanomagnets, including periodic networks of interconnected magnetic nanowires. Structurally similar to optical or acoustic metamaterials, these arrays could represent magnetic variants of such artificial materials. Using micromagnetic simulations, we investigate a three-dimensional array of interconnected magnetic nanowires with intersection points corresponding to atomic positions of a diamond lattice. The high-frequency excitation spectrum of this artificial magnetic crystal (AMC) is governed by its microstructure and, to a lesser extent, by the magnetic configuration. The magnetic system displays characteristics of three-dimensional artificial spin ice. It can contain Dirac-type magnetic defect structures, which modify the magnonic spectrum of the AMC similarly as defect sites in a natural diamond crystal influence optical absorption spectra. Our study opens new perspectives for applying such materials in high-density magnonic devices and shows that AMCs represent a promising category of magnonic materials with tunable properties.

Topological fine structure of an energy band. (arXiv:2312.08436v1 [cond-mat.mes-hall])
Hui Liu, Cosma Fulga, Emil J. Bergholtz, Janos Asboth

A band with a nonzero Chern number cannot be fully localized by weak disorder. There must remain at least one extended state, which ``carries the Chern number.'' Here we show that a trivial band can behave in a similar way. Instead of fully localizing, arbitrarily weak disorder leads to the emergence of two sets of extended states, positioned at two different energy intervals, which carry opposite Chern numbers. Thus, a single trivial band can show the same behavior as two separate Chern bands. We show that this property is predicted by a topological invariant called a ``localizer index.'' Even though the band as a whole is trivial as far as the Chern number is concerned, the localizer index allows access to a topological fine structure. This index changes as a function of energy within the bandwidth of the trivial band, causing nontrivial extended states to appear as soon as disorder is introduced. Our work points to a previously overlooked manifestation of topology, which impacts the response of systems to impurities beyond the information included in conventional topological invariants.

Majorana modes in striped two-dimensional inhomogeneous topological superconductors. (arXiv:2312.08439v1 [cond-mat.mes-hall])
Pasquale Marra, Daisuke Inotani, Takeshi Mizushima, Muneto Nitta

Majorana zero modes have gained significant interest due to their potential applications in topological quantum computing and in the realization of exotic quantum phases. These zero-energy quasiparticle excitations localize at the vortex cores of two-dimensional topological superconductors or at the ends of one-dimensional topological superconductors. Here we describe an alternative platform: a two-dimensional topological superconductor with inhomogeneous superconductivity, where Majorana modes localize at the ends of topologically nontrivial one-dimensional stripes induced by the spatial variations of the order parameter phase. In certain regimes, these Majorana modes hybridize into a single highly nonlocal state delocalized over spatially separated points, with exactly zero energy at finite system sizes and with emergent quantum-mechanical supersymmetry. We then present detailed descriptions of braiding and fusion protocols and showcase the versatility of our proposal by suggesting possible setups which can potentially lead to the realization Yang-Lee anyons and the Sachdev-Ye-Kitaev model.

Emergent Fermion Dynamical Symmetry for Monolayer Graphene in a Strong Magnetic Field. (arXiv:2312.08475v1 [cond-mat.mes-hall])
Mike Guidry, Lianao Wu, Fletcher Williams

We review the physics of monolayer graphene in a strong magnetic field, with emphasis on highly collective states that emerge from the weakly interacting system because of correlations (emergent states). After reviewing the general properties of graphene and of electrons in a magnetic field, we give a brief introduction to the integer quantum Hall effect (IQHE) and the fractional quantum Hall effect (FQHE) in a 2D electron gas as foundation to show that monolayer graphene in a magnetic field exhibits both effects, but with properties modified by the influence of the graphene crystal. After giving an introduction to standard methods of dealing with emergent states for this system, we show that an SO(8) fermion dynamical symmetry governs the emergent degrees of freedom and that the algebraic and group properties of the dynamical symmetry provide a new view of strongly correlated states observed in monolayer graphene subject to a strong magnetic field.

Crystalline finite-size topology. (arXiv:2312.08552v1 [cond-mat.str-el])
Michał J. Pacholski, Ashley M. Cook

Topological phases stabilized by crystalline point group symmetry protection are a large class of symmetry-protected topological phases subjected to considerable experimental scrutiny. Here, we show that the canonical three-dimensional (3D) crystalline topological insulator protected by time-reversal symmetry $\mathcal{T}$ and four-fold rotation symmetry $\mathcal{C}_4$ individually or the product symmetry $\mathcal{C}_4 \mathcal{T}$, generically realizes finite-size crystalline topological phases in thin film geometry (a quasi-(3-1)-dimensional, or q(3-1)D, geometry): response signatures of the 3D bulk topology co-exist with topologically-protected, quasi-(3-2)D and quasi-(3-3)D boundary modes within the energy gap resulting from strong hybridisation of the Dirac cone surface states of the underlying 3D crystalline topological phase. Importantly, we find qualitative distinctions between these gapless boundary modes and those of strictly 2D crystalline topological states with the same symmetry-protection, and develop a low-energy, analytical theory of the finite-size topological magnetoelectric response.

Measuring entanglement entropy and its topological signature for phononic systems. (arXiv:2312.08632v1 [quant-ph])
Zhi-Kang Lin, Yao Zhou, Bin Jiang, Bing-Quan Wu, Li-Mei Chen, Xiao-Yu Liu, Li-Wei Wang, Peng Ye, Jian-Hua Jiang

Entanglement entropy is a fundamental concept with rising importance in different fields ranging from quantum information science, black holes to materials science. In complex materials and systems, entanglement entropy provides insight into the collective degrees of freedom that underlie the systems' complex behaviours. As well-known predictions, the entanglement entropy exhibits area laws for systems with gapped excitations, whereas it follows the Gioev-Klich-Widom scaling law in gapless fermion systems. Furthermore, the entanglement spectrum provides salient characterizations of topological phases and phase transitions beyond the conventional paradigms. However, many of these fundamental predictions have not yet been confirmed in experiments due to the difficulties in measuring entanglement entropy in physical systems. Here, we report the experimental verification of the above predictions by probing the nonlocal correlations in phononic systems. From the pump-probe responses in phononic crystals, we obtain the entanglement entropy and entanglement spectrum for phononic systems with the fermion filling analog. With these measurements, we verify the Gioev-Klich-Widom scaling law of entanglement entropy for various quasiparticle dispersions in one- and two-dimensions. Moreover, we observe the salient signatures of topological phases in the entanglement spectrum and entanglement entropy which unveil an unprecedented probe of topological phases without relying on the bulk-boundary correspondence. The progress here opens a frontier where entanglement entropy serves as an important experimental tool in the study of emergent phases and phase transitions which can be generalized to non-Hermitian and other unconventional regimes.

Unlocking High Performance, Ultra-Low Power Van der Waals Transistors: Towards Back-End-of-Line In-Sensor Machine Vision Applications. (arXiv:2312.08634v1 [cond-mat.mtrl-sci])
Olaiyan Alolaiyan, Shahad Albwardi, Sarah Alsaggaf, Thamer Tabbakh, Frank W. DelRio, Moh. R. Amer

Recent reports on machine learning (ML) and machine vision (MV) devices have demonstrated the potentials of 2D materials and devices. Yet, scalable 2D devices are being challenged by contact resistance and Fermi Level Pinning (FLP), power consumption, and low-cost CMOS compatible lithography processes. To enable CMOS+2D, it is essential to find a proper lithography strategy that can fulfill these requirements. Here, we explore modified van der Waals (vdW) deposition lithography and demonstrate a relatively new class of van-der-Waals-Field-Effect-Transistors (vdW-FETs) based on 2D materials. This lithography strategy enables us to unlock high performance devices evident by high current on-off ratio (Ion/Ioff), high turn-on current density (Ion), and weak Fermi Level Pinning (FLP). We utilize this approach to demonstrate a gate-tunable near-ideal diode using MoS2/WSe2 heterojunction with an ideality factor of ~1.65 and current rectification of 102. We finally demonstrate a highly sensitive, scalable, and ultra-low power phototransistor using MoS2/ WSe2 vdW-FET for Back-End-of-Line (BEOL) integration. Our phototransistor exhibits the highest gate-tunable photoresponsivity achieved to date for white light detection with ultra-low power dissipation, enabling ultra-sensitive, ultra-fast, and efficient optoelectronic applications such as in-sensor neuromorphic machine vision. Our approach shows the great potential of modified vdW deposition lithography for back-end-of-line CMOS+2D applications.

Nonlinear optical responses in multi-orbital topological superconductors. (arXiv:2312.08638v1 [cond-mat.supr-con])
Arpit Raj, Abigail Postlewaite, Swati Chaudhary, Gregory A. Fiete

We theoretically study first and second-order optical responses in a transition metal dichalcogenide monolayer with distinct trivial, nodal, and time-reversal invariant topological superconducting (TRITOPS) phases. We show that the second-order DC response, also known as the photogalvanic response, contains signatures for differentiating these phases while the first-order optical response does not. We find that the high-frequency photogalvanic response is insensitive to the phase of the system, while the low-frequency response exhibits features distinguishing the three phases. At zero doping, corresponding to an electron filling in which the Fermi level lies at nodal points, there are opposite sign zero-frequency divergences in the response when approaching the nodal phase boundaries from the trivial and the TRITOPS phases. In the trivial phase, both the high-frequency and low-frequency response of the system are negative, but in the TRITOPS phase, the low-frequency response becomes positive while the high-frequency response remains negative. Furthermore, since phase transitions are controlled by the Rashba spin-orbit coupling and the ratio of intra-orbital and inter-orbital paring amplitudes, our results not only help distinguish the phases but can also provide an estimate of the pairing amplitudes based on the photogalvanic response of the system.

Electric-Field-Induced Domain Walls in Wurtzite Ferroelectrics. (arXiv:2312.08645v1 [cond-mat.mtrl-sci])
Ding Wang, Danhao Wang, Mahlet Molla, Yujie Liu, Samuel Yang, Mingtao Hu, Jiangnan Liu, Yuanpeng Wu, Tao Ma, Emmanouil Kioupakis, Zetian Mi

Wurtzite ferroelectrics hold transformative potential for next-generation microelectronics. However, fundamental atomic-level understanding of their intrinsic switching mechanisms and domain energetics remains elusive. By combining scanning transmission electron microscopy and density functional theory, we reveal sub-nanometer electric-field-induced domain walls in a representative wurtzite ferroelectric, ScGaN. We observe vertical domain walls with side-by-side antiparallel polarization and, significantly, a new type of horizontal domain wall featuring a novel "2H MoS2-like" configuration. Such configuration substantiates a buckled hexagonal phase with large polarization discontinuity and rich dangling bonds, offering a new framework for domain wall electronics. Our findings mark a pivotal step in understanding ferroelectric domain switching in this emerging material class and lay the groundwork for fundamental physics studies and innovative device applications based on wurtzite ferroelectrics.

Real-time Autonomous Control of a Continuous Macroscopic Process as Demonstrated by Plastic Forming. (arXiv:2312.08658v1 [cond-mat.soft])
Shun Muroga, Takashi Honda, Yasuaki Miki, Hideaki Nakajima, Don N. Futaba, Kenji Hata

To meet the demands for more adaptable and expedient approaches to augment both research and manufacturing, we report an autonomous system using real-time in-situ characterization and an autonomous, decision-making processer based on an active learning algorithm. This system was applied to a plastic film forming system to highlight its efficiency and accuracy in determining the process conditions for specified target film dimensions, importantly, without any human intervention. Application of this system towards nine distinct film dimensions demonstrated the system ability to quickly determine the appropriate and stable process conditions (average 11 characterization-adjustment iterations, 19 minutes) and the ability to avoid traps, such as repetitive over-correction. Furthermore, comparison of the achieved film dimensions to the target values showed a high accuracy (R2 = 0.87, 0.90) for film width and thickness, respectively. In addition, the use of an active learning algorithm afforded our system to proceed optimization with zero initial training data, which was unavailable due to the complex relationships between the control factors (material supply rate, applied force, material viscosity) within the plastic forming process. As our system is intrinsically general and can be applied to any most material processes, these results have significant implications in accelerating both research and industrial processes.

Confinement of electron holes via the peroxo group formation in the negative charge-transfer materials on the example of SrFeO3: plane-wave density functional theory predictions. (arXiv:2312.08665v1 [cond-mat.mtrl-sci])
Nikita A. Afimchenko, Aleksandr A. Shubin, Igor L. Zilberberg, Alexander P. Nemudry

The present work puts forward a concept that the thermostable O1s XPS peaks with energy of about 531 eV in negative charge-transfer SrFeO_{3-\delta} perovskite are determined by the peroxo-like oxygen species. The peroxo group forms via coupling two oxygen anions coordinated to iron cations with d^5\bar-under{L} (\bar-under{L}-oxygen electron hole) configuration. By means of plane-wave DFT+U approach there have been shown that the peroxo group represents a metastable state in the absence of oxygen vacancies nearby. The O-O bonding confines two electron holes freezing the 3+ oxidation state for two iron cations bridged by peroxide. Increasing the peroxo group numbers makes the ferrite a semiconductor with charge-transfer gap of about 0.6 eV.

Magneto-optical effects of an artificially-layered ferromagnetic topological insulator. (arXiv:2312.08687v1 [cond-mat.mtrl-sci])
Xingyue Han, Hee Taek Yi, Seongshik Oh, Liang Wu

Magnetic topological insulator is a fertile platform to study the interplay between magnetism and topology. The unique electronic band structure can induce exotic transport and optical properties. However, a comprehensive optical study in both near-infrared frequency and terahertz frequency has been lacking. Here, we report magneto-optical effects from a heterostructure of Cr-incorporated topological insulator, CBST. We use 800 nm magneto-optical Kerr effect to reveal a ferromagnetic order in the CBST film with a high transition temperature at 160 K. We also use time-domain terahertz polarimetry to reveal a terahertz Faraday rotation of 1.5 mrad and Kerr rotation of 5.1 mrad at 2 K. The calculated terahertz Hall conductance is 0.42 $e^2/h$. Our work shows the optical responses of an artificially layered magnetic topological insulator, paving the way towards high-temperature quantum anomalous Hall effect via heterostructure engineering.

Induced magneto-conductivity in a two-node Weyl semimetal under Gaussian random disorder. (arXiv:2312.08716v1 [cond-mat.mes-hall])
Chuan-Xiong Xu, Hao-Ping Yu, Mei Zhou, Xuanting Ji

Measuring the magnetoconductivity induced from impurities may help determine the impurity distribution and reveal the structure of a Weyl semimetal sample. To verify this, we utilized the Gaussian random disorder to simulate charged impurities in a two-node Weyl semimetal model and investigate the impact of charged impurities on magnetoconductivity in Weyl semimetals. We first compute the longitudinal magnetic conductivity and find that it is positive and increases proportionally with the parameter governing the Gaussian distribution of charged impurities, suggesting the presence of negative longitudinal magnetoresistivity (NLMR). Then we consider both the intravalley and inter-valley scattering processes to calculate the induced transverse magnetoconductivity in the model. Our findings indicate that both inter-valley and intra-valley scattering processes play important roles in calculating the transverse magnetoconductivity. The locations of Weyl nodes can also be determined by magnetoconductivity measurements. This is possible if the magnetic field strength and the density of charged impurities are known. Alternatively, the measurement of magnetic conductivity may reveal the distribution of charged impurites in a given sample once the locations of the Weyl nodes have been determined. These findings can aid in detecting the structure of a Weyl semimetal sample, enhancing comprehension of magnetotransport in Weyl semimetals, and promoting the development of valley electronics.

Structure-driven phase transitions in paracrystalline topological insulators. (arXiv:2312.08779v1 [cond-mat.mes-hall])
Victor Regis, Victor Velasco, Marcello B. Silva Neto, Caio Lewenkopf

We study phase transitions driven by structural disorder in noncrystalline topological insulators. We introduce a procedural generation algorithm, the Perlin noise, typically used in computer graphics, to incorporate disorder to a two-dimensional lattice, allowing a continuous interpolation between a pristine and a random gas system, going through all different intermediate structural regimes, such as the paracrystalline and the amorphous phases. We define a two-band model, including intraorbital and interorbital mixings, on the structures generated by the algorithm and we find a sequence of structure-driven topological phase transitions characterized by changes in the topological Bott index, at which the insulating gap dynamically closes while evolving from the Bragg planes of the Brillouin zone towards the center. We interpret our results within the framework of Hosemann's paracrystal theory, in which distortion is included in the lattice structure factor and renormalizes the band-splitting parameter. Based on these results, we ultimately demonstrate the phenomenon of topological protection at its extreme.

Automated Structure Discovery for Scanning Tunneling Microscopy. (arXiv:2312.08854v1 [cond-mat.mtrl-sci])
Lauri Kurki, Niko Oinonen, Adam S. Foster

Scanning tunnelling microscopy (STM) with a functionalized tip apex reveals the geometric and electronic structure of a sample within the same experiment. However, the complex nature of the signal makes images difficult to interpret and has so far limited most research to planar samples with a known chemical composition. Here, we present automated structure discovery for STM (ASD-STM), a machine learning tool for predicting the atomic structure directly from an STM image, by building upon successful methods for structure discovery in non-contact atomic force microscopy (nc-AFM). We apply the method on various organic molecules and achieve good accuracy on structure predictions and chemical identification on a qualitative level, while highlighting future development requirements to ASD-STM. This method is directly applicable to experimental STM images of organic molecules, making structure discovery available for a wider SPM audience outside of nc-AFM. This work also opens doors for more advanced machine learning methods to be developed for STM discovery.

Insulator-to-metal Mott transition facilitated by lattice deformation in monolayer $\alpha$-RuCl$_3$ on graphite. (arXiv:2312.08918v1 [cond-mat.str-el])
Xiaohu Zheng, Ogasawara Takuma, Huaxue Zhou, Chongli Yang, Xin Han, Gang Wang, Junhai Ren, Youguo Shi, Katsumi Tanigaki, Rui-Rui Du

Creating heterostructures with graphene/graphite is a practical method for charge-doping $\alpha$-RuCl$_3$, but not sufficient to cause the insulator-to-metal transition. In this study, detailed scanning tunneling microscopy/spectroscopy measurements on $\alpha$-RuCl$_3$ with various lattice deformations reveal that both in-plane and out-of-plane lattice distortions may collapse the Mott-gap in the case of monolayer $\alpha$-RuCl$_3$ in proximity to graphite, but have little impact on its bulk form alone. In the Mott-Hubbard framework, the transition is attributed to the lattice distortion-facilitated substantial modulation of the electron correlation parameter. Observation of the orbital textures on a highly compressed monolayer $\alpha$-RuCl$_3$ flake on graphite provides valuable evidence that electrons are efficiently transferred from the heterointerface into Cl3$p$ orbitals under the lattice distortion. It is believed that the splitting of Ru $t_{2g}$ bands within the trigonal distortion of Ru-Cl-Ru octahedra bonds generated the electrons transfer pathways. The increase of the Cl3$p$ states enhance the hopping integral in the Mott-Hubbard bands, resulting in the Mott-transition. These findings suggest a new route for implementing the insulator-to-metal transition upon doping in $\alpha$-RuCl$_3$ by deforming the lattice in addition to the formation of heterostructure.

A universal shortcut method for state transfer in quantum spin systems. (arXiv:2312.08920v1 [quant-ph])
Jian Xu, Feng Mei, Yan-Qing Zhu

The need for fast and robust quantum state transfer is an essential element in scalable quantum information processing, leading to widespread interest in shortcuts to adiabaticity for speeding up adiabatic quantum protocols. However, shortcuts to adiabaticity for systems with more than a few levels is occasionally challenging to compute in theory and frequently difficult to implement in experiments. In this work, we develop a protocol for constructing shortcuts to adiabaticity through the multi-state Landau-Zener approach and a stricter adiabatic condition. Importantly, our protocol only requires a few pieces of information about the energy spectrum and adjusts the evolutionary rate of the system, making it both generic for theoretical models and friendly for experimental implementation. As examples, we apply our protocol to state transfer in the non-Hermitian Su-Schrieffer-Heeger (SSH) model and the topological Thouless pump models and find that it can speed up the manipulation speed while remaining robust to Hamiltonian errors. Furthermore, our findings can be realized using current technology and could potentially be extended to many-body systems, dissipation cases, or Floquet processes. Overall, the proposed shortcut protocol offers a promising avenue for enhancing the efficiency and reliability of quantum state transfer protocols.

Layer topology of smectic grain boundaries. (arXiv:2312.08964v1 [cond-mat.soft])
René Wittmann

Grain boundaries in extremely confined colloidal smectics possess a topological fine structure with coexisting nematic and tetratic symmetry of the director field. An alternative way to approach the problem of smectic topology is via the layer structure, which is typically more accessible in experiments on molecular liquid crystals. Here, we translate the concept of endpoint defects, which appear as tetratic disclinations of quarter charge in director topology, to layer topology for two-dimensional smectics. By doing so, we elaborate on further advantages of a topological concept evolving around the layer structure rather than the director field, such as providing insight in the structure of edge dislocations or virtual defects at the confining walls.

Melting of unidirectional charge density waves across twin domain boundaries in GdTe$_{3}$. (arXiv:2312.08986v1 [cond-mat.str-el])
Sanghun Lee, Eunseo Kim, Junho Bang, Jongho Park, Changyoung Kim, Dirk Wulferding, Doohee Cho

Solids undergoing a transition from order to disorder experience the proliferation of topological defects. The melting process generates transient quantum states. However, their dynamical nature with femtosecond lifetime hinders exploration with atomic precision. Here, we suggest an alternative approach to the dynamical melting process by focusing on the interface created by competing degenerate quantum states. We use a scanning tunneling microscope (STM) to visualize the unidirectional charge density wave (CDW) and its spatial progression ("static melting") across a twin domain boundary (TDB) in the layered material GdTe$_{3}$. Combining STM with a spatial lock-in technique, we reveal that the order parameter amplitude attenuates with the formation of dislocations and thus two different unidirectional CDWs coexist near the TDB, reducing the CDW anisotropy. Notably, we discover a correlation between this anisotropy and the CDW gap. Our study provides valuable insight into the behavior of topological defects and transient quantum states.

Tailoring Amorphous Boron Nitride for High-Performance 2D Electronics. (arXiv:2312.09136v1 [cond-mat.mtrl-sci])
Cindy Y. Chen (1), Zheng Sun (2), Riccardo Torsi (1), Ke Wang (3), Jessica Kachian (4), Bangzhi Liu (3), Gilbert B. Rayner Jr (5), Zhihong Chen (2), Joerg Appenzeller (2), Yu-Chuan Lin (6), Joshua A. Robinson (1, 3, 7) ((1) Department of Materials Science and Engineering, The Pennsylvania State University, (2) School of Electrical and Computer Engineering and Birck Nanotechnology Center, Purdue University, (3) Materials Research Institute, The Pennsylvania State University, (4) Intel Corporation, (5) The Kurt J. Lesker Company, (6) Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, (7) Two-Dimensional Crystal Consortium, The Pennsylvania State University)

Two-dimensional (2D) materials have garnered significant attention in recent years due to their atomically thin structure and unique electronic and optoelectronic properties. To harness their full potential for applications in next-generation electronics and photonics, precise control over the dielectric environment surrounding the 2D material is critical. The lack of nucleation sites on 2D surfaces to form thin, uniform dielectric layers often leads to interfacial defects that degrade the device performance, posing a major roadblock in the realization of 2D-based devices. Here, we demonstrate a wafer-scale, low-temperature process (< 250 {\deg}C) using atomic layer deposition (ALD) for the synthesis of uniform, conformal amorphous boron nitride (aBN) thin films. ALD deposition temperatures between 125 and 250 {\deg}C result in stoichiometric films with high oxidative stability, yielding a dielectric strength of 8.2 MV/cm. Utilizing a seed-free ALD approach, we form uniform aBN dielectric layers on 2D surfaces and fabricate multiple quantum well structures of aBN/MoS2 and aBN-encapsulated double-gated monolayer (ML) MoS2 field-effect transistors to evaluate the impact of aBN dielectric environment on MoS2 optoelectronic and electronic properties. Our work in scalable aBN dielectric integration paves a way towards realizing the theoretical performance of 2D materials for next-generation electronics.

Nonlocal damping of spin waves in a magnetic insulator induced by normal, heavy, or altermagnetic metallic overlayer: a Schwinger-Keldysh field theory approach. (arXiv:2312.09140v1 [cond-mat.mes-hall])
Felipe Reyes-Osorio, Branislav K. Nikolic

Understanding spin wave (SW) damping, and how to control it to the point of being able to amplify SW-mediated signals, is one of the key requirements to bring the envisaged magnonic technologies to fruition. Even widely used magnetic insulators with low magnetization damping in their bulk, such as yttrium iron garnet, exhibit 100-fold increase in SW damping due to inevitable contact with metallic layers in magnonic circuits, as observed in very recent experiments [I. Bertelli et al., Adv. Quantum Technol. 4, 2100094 (2021)] mapping SW damping in spatially-resolved fashion. Here, we provide microscopic and rigorous understanding of wavevector-dependent SW damping using extended Landau-Lifshitz-Gilbert equation with nonlocal damping tensor, instead of conventional local scalar Gilbert damping, as derived from Schwinger-Keldysh nonequilibrium quantum field theory. In this picture, the origin of nonlocal magnetization damping and thereby induced wavevector-dependent SW damping is interaction of localized magnetic moments of magnetic insulator with conduction electrons from the examined three different types of metallic overlayers -- normal, heavy, and altermagnetic. Due to spin-split energy-momentum dispersion of conduction electrons in the latter two cases, the nonlocal damping is anisotropic in spin and space, and it can be dramatically reduced by changing the relative orientation of the two layers when compared to the usage of normal metal overlayer.

Observable-enriched entanglement. (arXiv:2312.09153v1 [quant-ph])
Joe H. Winter, Reyhan Ay, Bernd Braunecker, A. M. Cook

We introduce methods of characterizing entanglement, in which entanglement measures are enriched by the matrix representations of operators for observables. These observable operator matrix representations can enrich the partial trace over subsets of a system's degrees of freedom, yielding reduced density matrices useful in computing various measures of entanglement, which also preserve the observable expectation value. We focus here on applying these methods to compute observable-enriched entanglement spectra, unveiling new bulk-boundary correspondences of canonical four-band models for topological skyrmion phases and their connection to simpler forms of bulk-boundary correspondence. Given the fundamental roles entanglement signatures and observables play in study of quantum many body systems, observable-enriched entanglement is broadly applicable to myriad problems of quantum mechanics.

Giant chirality-induced spin polarization in twisted transition metal dichalcogenides. (arXiv:2312.09169v1 [cond-mat.mes-hall])
Guido Menichetti, Lorenzo Cavicchi, Leonardo Lucchesi, Fabio Taddei, Giuseppe Iannaccone, Pablo Jarillo-Herrero, Frank H. L. Koppens, Marco Polini

Chirality-induced spin selectivity (CISS) is an effect that has recently attracted a great deal of attention in chiral chemistry and that remains to be understood. In the CISS effect, electrons passing through chiral molecules acquire a large degree of spin polarization. In this Letter we show that this effect can be spectacularly large in atomically-thin chiral crystals created by van der Waals assembly, provided they are spin-orbit coupled. Its origin stems from the combined effects of structural chirality and spin-flipping spin-orbit coupling. We present detailed calculations for twisted homobilayer transition metal dichalcogenides, showing that the chirality-induced spin polarization can be giant, e.g. easily exceeding $50\%$ for ${\rm MoTe}_2$. Our results clearly indicate that twisted quantum materials can operate as a fully tunable platform for the study and control of the CISS effect in condensed matter physics and chiral chemistry.

Self-organisation of auto-phoretic suspensions in confined shear flows. (arXiv:2312.09178v1 [cond-mat.soft])
Prathmesh Vinze, Sebastien Michelin

Janus phoretic particles exploit chemical energy stored in their environment to self-propel. These active particles modify and respond to their hydrodynamic and chemical environments, thus giving them a sensibility to external flows and other particles. Furthermore, experimental observations and analysis on biological or synthetic active suspensions indicate that hydro-chemical interparticle interactions lead to non-trivial collective behaviour (e.g., cluster formation of phoretic particles or bacterial swarming) and that the response of the suspensions to shear flows is non-trivial. In fact, it can lead to significant reductions in viscosity due to the energy conversion at microscopic scales. In this work, using simulations of a continuum kinetic model, we analyse the dynamics and response to shear and confinement of dilute suspensions of chemotactic phoretic particles that reorient and drift toward the chemical solutes released by their neighbours. We show that a 1D transient steady distribution driven by the effect of confinement is a common feature considered and analyse its stability for varying confinement strength and shear rate. In the second step, we consider and discuss, more specifically, the feedback effect on the flow by the particle and the resulting effective viscosity of the suspension.

Fractional corner charges induced by fragile topology in threefold symmetric two-dimensional materials. (arXiv:2312.09240v1 [cond-mat.mes-hall])
Olga Arroyo-Gascon, Sergio Bravo, Leonor Chico, Monica Pacheco

We perform a systematic study of the signatures of fragile topology in a number of nonmagnetic two-dimensional materials belonging to space group 164, most of them transition metal dichalcogenides. Using group theory analysis in the framework of topological quantum chemistry, we find fragile bands near the Fermi level for all the materials studied. Since stable topological bands are also present in these systems, the interplay of both phases is discussed, showing that corner charges appear in nearly three quarters of the materials and that they are caused by fragile topology. Using first-principles calculations, we predict corner states with fractional corner charges protected by C3 symmetry. Our work aims to broaden the scope of materials with experimentally accessible fragile bands.

Influence of N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) Structure Directing Agent on Al Pair Distributions and Features in Chabazite Zeolite. (arXiv:2110.12523v5 [cond-mat.mtrl-sci] UPDATED)
Xiaoyu Wang, Yujia Wang, Ahmad Moini, Rajamani Gounder, Edward J. Maginn, William F. Schneider

While organic structure directing agents (OSDAs) are well known to have a directional influence on the topology of a crystallizing zeolite, the relationship between OSDA charge and siting of aliovalent ions on a primarily siliceous framework is unclear. Here, we explore the relationship between OSDA orientation, Al3+ siting, and lattice energy, taking as a model system CHA zeolite occluded with N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) at an Si/Al ratio of 11/1. We use density functional theory calculations to parametrize a fixed-charge classical model describing van der Waals and electrostatic interactions between framework and OSDA. We enumerate and explore all possible combinations of OSDA orientation and Al location (attending to Lowenstein's rule) within a 36 T-site supercell. We find that interaction energies vary over 60 kJ/double-six-ring-unit (d6r). Further, analysis of configurations reveals that energies are sensitive to Al-Al proximity, such that low energies are associated with Al3+ pairs in 8-membered rings and higher energies associated with Al3+ pairs in smaller 6- and 4-membered rings. Comparisons with Al siting inferred from CHA zeolite crystallized with TMAda+ suggests that these computed interaction energies are useful reporters of observed Al siting in CHA synthesized with TMAda+.

Intraspecific predator interference promotes biodiversity in ecosystems. (arXiv:2112.05098v4 [q-bio.PE] UPDATED)
Ju Kang, Shijie Zhang, Xin Wang

Explaining biodiversity is a fundamental issue in ecology. A long-standing puzzle lies in the paradox of the plankton: many species of plankton feeding on a limited type of resources coexist, apparently flouting the competitive exclusion principle (CEP), which holds that the number of predator (consumer) species cannot exceed that of the resources at steady state. Here, we present a mechanistic model and show that the intraspecific interference among the consumers enables a plethora of consumer species to coexist at constant population densities with only one or a handful of resource species. The facilitated biodiversity is resistant to stochasticity, either with the stochastic simulation algorithm or individual-based modeling. Our model naturally explains the classical experiments that invalidate CEP, quantitatively illustrates the universal S-shaped pattern of the rank-abundance curves across a wide range of ecological communities, and can be broadly used to resolve the mystery of biodiversity in many natural ecosystems.

Discovery of a Single-Band Mott Insulator in a van der Waals Flat-Band Compound. (arXiv:2205.11462v3 [cond-mat.str-el] UPDATED)
Shunye Gao, Shuai Zhang, Cuixiang Wang, Shaohua Yan, Xin Han, Xuecong Ji, Wei Tao, Jingtong Liu, Tiantian Wang, Shuaikang Yuan, Gexing Qu, Ziyan Chen, Yongzhao Zhang, Jierui Huang, Mojun Pan, Shiyu Peng, Yong Hu, Hang Li, Yaobo Huang, Hui Zhou, Sheng Meng, Liu Yang, Zhiwei Wang, Yugui Yao, Zhiguo Chen, Ming Shi, Hong Ding, Huaixin Yang, Kun Jiang, Yunliang Li, Hechang Lei, Youguo Shi, Hongming Weng, Tian Qian

The Mott insulator provides an excellent foundation for exploring a wide range of strongly correlated physical phenomena, such as high-temperature superconductivity, quantum spin liquid, and colossal magnetoresistance. A Mott insulator with the simplest degree of freedom is an ideal and highly desirable system for studying the fundamental physics of Mottness. In this study, we have unambiguously identified such an anticipated Mott insulator in a van der Waals layered compound Nb3Cl8. In the high-temperature phase, where interlayer coupling is negligible, density functional theory calculations for the monolayer of Nb3Cl8 suggest a half-filled flat band at the Fermi level, whereas angle-resolved photoemission spectroscopy experiments observe a large gap. This observation is perfectly reproduced by dynamical mean-field theory calculations considering strong electron correlations, indicating a correlation-driven Mott insulator state. Since this half-filled band derived from a single 2a1 orbital is isolated from all other bands, the monolayer of Nb3Cl8 is an ideal realization of the celebrated single-band Hubbard model. Upon decreasing the temperature, the bulk system undergoes a phase transition, where structural changes significantly enhance the interlayer coupling. This results in a bonding-antibonding splitting in the Hubbard bands, while the Mott gap remains dominant. Our discovery provides a simple and seminal model system for investigating Mott physics and other emerging correlated states.

Renormalization approach to the analysis and design of Hermitian and non-Hermitian interfaces. (arXiv:2208.14626v2 [cond-mat.mes-hall] UPDATED)
Henning Schomerus

I describe a concrete and efficient real-space renormalization approach that provides a unifying perspective on interface states in a wide class of Hermitian and non-Hermitian models, irrespective of whether they obey a traditional bulk-boundary principle or not. The emerging interface physics are governed by a flow of microscopic interface parameters, and the properties of interface states become linked to the fixed-point topology of this flow. In particular, the quantization condition of interface states converts identically into the question of the convergence to unstable fixed points. As its key merit, the approach can be directly applied to concrete models and utilized to design interfaces that induce states with desired properties, such as states with a predetermined and possibly symmetry-breaking energy. I develop the approach in general, and then demonstrate these features in various settings, including for the design of circular, triangular and square-shaped complex dispersion bands and associated arcs at the edge of a two-dimensional system. Furthermore, I describe how this approach transfers to nonlinear settings, and demonstrate the efficiency, practicability and consistency of this extension for a paradigmatic model of topological mode selection by distributed saturable gain and loss.

Josephson Diode Effect Induced by Valley Polarization in Twisted Bilayer Graphene. (arXiv:2211.14846v4 [cond-mat.supr-con] UPDATED)
Jin-Xin Hu, Zi-Ting Sun, Ying-Ming Xie, K. T. Law

Recently, the Josephson diode effect (JDE), in which the superconducting critical current magnitudes differ when the currents flow in opposite directions, has attracted great interest. In particular, it was demonstrated that gate-defined Josephson junctions based on magic-angle twisted bilayer graphene showed a strong nonreciprocal effect when the weak-link region is gated to a correlated insulating state at half-filling (two holes per moir\'e cell). However, the mechanism behind such a phenomenon is not yet understood. In this work, we show that the interaction-driven valley polarization, together with the trigonal warping of the Fermi surface, induce the JDE. The valley polarization, which lifts the degeneracy of the states in the two valleys, induces a relative phase difference between the first and the second harmonics of supercurrent and results in the JDE. We further show that the nontrivial current phase relation, which is responsible for the JDE, also generates the asymmetric Shapiro steps.

Carbon Kagome Nanotubes -- quasi-one-dimensional nanostructures with flat bands. (arXiv:2301.10200v3 [cond-mat.mtrl-sci] UPDATED)
Hsuan Ming Yu, Shivam Sharma, Shivang Agarwal, Olivia Liebman, Amartya S. Banerjee

We introduce carbon Kagome nanotubes (CKNTs) -- a new allotrope of carbon formed by rolling up sheets of Kagome graphene, and investigate the properties of this material using first principles calculations. Based on the direction of rolling, we identify two principal varieties of CKNTs -- armchair and zigzag, and find that the bending stiffness associated with rolling Kagome graphene into either type of CKNT is about a third of that associated with rolling conventional graphene into carbon nanotubes (CNTs). Ab initio molecular dynamics simulations indicate that both types of CKNTs are likely to exist as stable structures at room temperature. Each CKNT explored here is metallic and features dispersionless states (i.e., flat bands) throughout its Brillouin zone, along with an associated singular peak in the electronic density of states, close to the Fermi level. We calculate the mechanical and electronic response of CKNTs to torsional and axial strains and compare against conventional CNTs. We show in particular, that upon twisting, degenerate dispersionless electronic states in CKNTs split, Dirac points and partially flat bands emerge from the quadratic band crossing point at the Fermi level, and that these features can be explained using a relatively simple tight-binding model.

Overall, CKNTs appear to be unique and striking examples of realistic elemental quasi-one-dimensional (1D) materials that can potentially display fascinating collective material properties arising from the presence of strongly correlated electrons. Additionally, distorted CKNTs may provide an interesting material platform where flat band physics and chirality induced anomalous transport effects may be studied together.

3D Ising CFT and Exact Diagonalization on Icosahedron: The Power of Conformal Perturbation Theory. (arXiv:2307.02540v4 [hep-th] UPDATED)
Bing-Xin Lao, Slava Rychkov

We consider the transverse field Ising model in $(2+1)$D, putting 12 spins at the vertices of the regular icosahedron. The model is tiny by the exact diagonalization standards, and breaks rotation invariance. Yet we show that it allows a meaningful comparison to the 3D Ising CFT on $\mathbb{R}\times S^2$, by including effective perturbations of the CFT Hamiltonian with a handful of local operators. This extreme example shows the power of conformal perturbation theory in understanding finite $N$ effects in models on regularized $S^2$. Its ideal arena of application should be the recently proposed models of fuzzy sphere regularization.

Can Majorana zero modes in quantum Hall edges survive edge reconstruction?. (arXiv:2308.01980v2 [cond-mat.mes-hall] UPDATED)
Kishore Iyer, Amulya Ratnakar, Sumathi Rao, Sourin Das

Parafermion zero modes can be trapped in the domain walls of quantum Hall edges proximitized by superconductors and ferromagnets. The $\nu = 1/3$ fractional quantum Hall side strip arising due to edge reconstruction of a $\nu = 1$ edge doubles the number of topological sectors such that each of them is $Z_{2} \times Z_{2}$ degenerate. The many-body spectrum displays a $4\pi$ Josephson periodicity, with the states in each $Z_{2}$ being energetically decoupled. Signatures of the new states appear in the fractional Josephson current when the edge velocities are taken to be different.

Anomalous Coherence Length in Superconductors with Quantum Metric. (arXiv:2308.05686v2 [cond-mat.supr-con] UPDATED)
Jin-Xin Hu, Shuai A. Chen, K. T. Law

The coherence length $\xi$ is a fundamental length scale of superconductors which governs the sizes of Cooper pairs, vortices, Andreev bound states and more. In existing microscopic theories of superconductivity, it is expected that as the attractive interaction increases, $\xi$ decreases as the electrons are bound together more strongly. In BCS theory, for example, the coherence length is $\xi_\mathrm{BCS} = \hbar v_{F}/\Delta$, where $v_{F}$ is the Fermi velocity and $\Delta$ is the pairing gap. It is clear that increasing $\Delta$ will shorten $\xi_\mathrm{BCS}$. However, the situation is puzzling for superconductors with completely flat bands in which $v_{F}$ goes to zero and $\xi_\mathrm{BCS}$ is expected to be zero. In this work, we show that the quantum metric, which is the real part of the quantum geometric tensor, gives rise to an anomalous contribution to the coherence length. Specifically, $\xi = \sqrt{\xi_\mathrm{BCS}^2 +\ell_{\mathrm{qm}}^{2}}$ for a superconductor where $\ell_{\mathrm{qm}}$ is the quantum metric contribution. In the flat band limit, $\xi$ does not vanish but bound by $\ell_{\mathrm{qm}}$. Incredibly, for the nontrivial flat bands with Chern number $C$, $\xi$ has a topological bound of $\xi\geq a\sqrt{\vert C \vert/4\pi}$ where $a$ is the lattice constant. Physically, the Cooper pair size of a superconductor cannot be squeezed down to a size smaller than $\ell_{\mathrm{qm}}$ which is a fundamental length scale determined by the quantum geometry of the bands. Finally, we calculate the quantum metric contributions for the superconducting moir\'e graphene family and show that the quantum metric effects are very important in these superconductors.

Majorana corner modes in unconventional monolayers of 1T-PtSe2 family. (arXiv:2308.12055v2 [cond-mat.mtrl-sci] UPDATED)
Haohao Sheng, Yue Xie, Quansheng Wu, Hongming Weng, Xi Dai, B. Andrei Bernevig, Zhong Fang, Zhijun Wang

In this work, we propose that Majorana zero modes can be realized at the corners of a topologically trivial insulator with unconventionality. We demonstrate that 1T-PtSe$_2$ is a symmetry indicator-free (SI-free) unconventional insulator, originating from orbital hybridization between Pt $d$ and Se $p_{x,y}$ states. The new kind of SI-free unconventionality has no symmetry eigenvalue indication. Instead, it is diagnosed directly by the Wannier charge centers by using the one-dimensional Wilson loop method. The obstructed edge states exhibit strong anisotropy and large Rashba splitting. By introducing superconducting proximity and external magnetic field, the Majorana corner modes can be obtained in 1T-PtSe$_2$ monolayer. In the end, we construct a two-Bernevig-Hughes-Zhang model with anisotropy to capture the Majorana physics.

Work statistics for Quantum Spin Chains: characterizing quantum phase transitions, benchmarking time evolution, and examining passivity of quantum states. (arXiv:2308.13366v3 [cond-mat.stat-mech] UPDATED)
Feng-Li Lin, Ching-Yu Huang

We study three aspects of work statistics in the context of the fluctuation theorem for the quantum spin chains by numerical methods based on matrix-product states. First, we elaborate that the work done on the spin-chain by a sudden quench can be used to characterize the quantum phase transitions (QPT). We further obtain the numerical results to demonstrate its capability of characterizing the QPT of both Landau-Ginzbrug types, such as the Ising chain, or topological types, such as the Haldane chain. Second, we propose to use the fluctuation theorem, such as Jarzynski's equality, which relates the real-time correlator to the ratio of the thermal partition functions, as a benchmark indicator for the numerical real-time evolving methods. Third, we study the passivity of ground and thermal states of quantum spin chains under some cyclic impulse processes. We show that the passivity of thermal states and ground states under the hermitian actions are ensured by the second laws and variational principles, respectively, and also verify it by numerical calculations. Besides, we also consider the passivity of ground states under non-hermitian actions, for which the variational principle cannot be applied. Despite that, we find no violation of passivity from our numerical results for all the cases considered in both Ising-like and Haldane-like chains.

One-Half Topological Number in Entangled Quantum Physics. (arXiv:2308.14062v2 [cond-mat.mes-hall] UPDATED)
Karyn Le Hur

A topological phase can be engineered in quantum physics from the Bloch sphere of a spin-1/2 showing an 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 of one-half topological numbers. Similar to Cooper pairs in superconductors, the Einstein-Podolsky-Rosen pair or Bell state produces a half flux quantization, which here refers to the halved flux of the Berry curvature on the surface. These 1/2-numbers also reveal the presence of a free Majorana fermion at a pole. The topological responses can be measured when driving from north to south and also from a circularly polarized field at the poles revealing the quantized or half-quantized nature of the protected transverse currents. We show applications of entangled wavefunctions in band structures, introducing a local topological marker in momentum space, to characterize the topological response of two-dimensional semimetals in bilayer geometries.

Spin-polarized transport properties in magnetic moir\'e superlattices. (arXiv:2308.14342v2 [cond-mat.mes-hall] UPDATED)
Zhao Gong, Qing-Qing Zhang, Hui-Ying Mu, Xing-Tao An, Jian-Jun Liu

Since the discovery of the fascinating properties in magic-angle graphene, the exploration of moir\'e systems in other two-dimensional materials has garnered significant attention and given rise to a field known as 'moir\'e physics'. Within this realm, magnetic van der Waals heterostructure and the magnetic proximity effect in moir\'e superlattices have also become subjects of great interest. However, the spin-polarized transport property in this moir\'e structures is still a problem to be explored. Here, we investigate the spin-polarized transport properties in a moir\'e superlattices formed by a two-dimensional ferromagnet CrI_3 stacked on a monolayer BAs, where the spin degeneracy is lifted because of the magnetic proximity effect associated with the moir\'e superlattices. We find that the conductance exhibits spin-resolved miniband transport properties at a small twist angle because of the periodic moir\'e superlattices. When the incident energy is in the spin-resolved minigaps, the available states are spin polarized, thus providing a spin-polarized current from the superlattice. Moreover, only a finite number of moir\'e period is required to obtain a net spin polarization of 100\%. In addition, the interlayer distance of the heterojunction is also moir\'e modifiable, so a perpendicular electric field can be applied to modulate the intensity and direction of the spin polarization. Our finding points to an opportunity to realize spin functionalities in magnetic moir\'e superlattices.

Percolation Transition in a Topological Phase. (arXiv:2309.06483v2 [cond-mat.dis-nn] UPDATED)
Saikat Mondal, Subrata Pachhal, Adhip Agarwala

Transition out of a topological phase is typically characterized by discontinuous changes in topological invariants along with bulk gap closings. However, as a clean system is geometrically punctured, it is natural to ask the fate of an underlying topological phase. To understand this physics we introduce and study both short and long-ranged toy models where a one dimensional topological phase is subjected to bond percolation protocols. We find that non-trivial boundary phenomena follow competing energy scales even while global topological response is governed via geometrical properties of the percolated lattice. Using numerical, analytical and appropriate mean-field studies we uncover the rich phenomenology and the various cross-over regimes of these systems. In particular, we discuss emergence of "fractured topological region" where an overall trivial system contains macroscopic number of topological clusters. Our study shows the interesting physics that can arise from an interplay of geometrical disorder within a topological phase.

Chern numbers for the two-body Hofstadter-Hubbard butterfly. (arXiv:2310.09565v2 [cond-mat.quant-gas] UPDATED)
D. C. Alyuruk, M. Iskin

We analyze the two-body spectrum within the Hofstadter-Hubbard model on a square lattice through an exact variational ansatz and study the topological properties of its low-lying two-body bound-state branches. In particular we discuss how the Hofstadter-Hubbard butterfly of the two-body branches evolves as a function of onsite interactions and how to efficiently calculate their Chern numbers using the Fukui-Hatsugai-Suzuki approach. Our numerical results are fully consistent with the simple picture that appears in the strong-coupling limit, where the attraction between fermions forms a composite boson characterized by an effective hopping parameter and an effective magnetic-flux ratio.

Torsion at different scales: from materials to the Universe. (arXiv:2310.13150v2 [gr-qc] UPDATED)
Nick E. Mavromatos, Pablo Pais, Alfredo Iorio

The concept of torsion in geometry, although known since long time, has not gained considerable attention by the physics community until relatively recently, due to its diverse and potentially important applications to a plethora of contexts of physical interest. These range from novel materials, such as graphene and graphene-like materials, to advanced theoretical ideas, such as string theory and supersymmetry/supergravity and applications thereof in understanding the dark sector of our Universe. This work reviews such applications of torsion at different physical scales.

Effects of domain walls and chiral supercurrent in quantum anomalous Hall Josephson junctions. (arXiv:2312.00331v2 [cond-mat.mes-hall] UPDATED)
Junjie Qi, Haiwen Liu, Jie Liu, Hua Jiang, Dong E. Liu, Chui-Zhen Chen, Ke He, X. C. Xie

The intriguing interplay between topology and superconductivity has attracted significant attention, given its potential for realizing topological superconductivity. In this study, we investigate the transport properties of the chiral Josephson effect in the quantum anomalous Hall insulators (QAHIs)-based junction. We reveal a systematic crossover from edge-state to bulk-state dominant supercurrents, with a notable $0-\pi$ transition observed under non-zero magnetic flux through chemical potential adjustments. This transition underscores the competition between bulk and chiral edge transport. Furthermore, we identify an evolution among three distinct quantum interference patterns: from a $2\Phi_0$-periodic oscillation pattern, to a $\Phi_0$-periodic oscillation pattern, and then to an asymmetric Fraunhofer pattern ($\Phi_0 = h/2e$ is the flux quantum, $h$ the Planck constant, and $e$ the electron charge). Subsequently, we examine the influence of domains on quantum interference patterns. Intriguingly, a distinctive Fraunhofer-like pattern emerges due to coexistence of chiral edge states and domain wall states, even when the chemical potential is within gap. These results not only advance the theoretical understanding but also pave the way for the experimental discovery of the chiral Josephson effect based on QAHI doped with magnetic impurities.

Found 9 papers in prb
Date of feed: Fri, 15 Dec 2023 04:17:06 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]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Topological phase detection through high-harmonic spectroscopy in extended Su-Schrieffer-Heeger chains
Mohit Lal Bera, Jessica O. de Almeida, Marlena Dziurawiec, Marcin Płodzień, Maciej M. Maśka, Maciej Lewenstein, Tobias Grass, and Utso Bhattacharya
Author(s): Mohit Lal Bera, Jessica O. de Almeida, Marlena Dziurawiec, Marcin Płodzień, Maciej M. Maśka, Maciej Lewenstein, Tobias Grass, and Utso Bhattacharya

Su-Schrieffer-Heeger (SSH) chains are paradigmatic examples of one-dimensional topological insulators hosting zero-energy edge modes when the bulk of the system has a nonzero topological winding invariant. Recently, high-harmonic spectroscopy has been suggested as a tool for detecting the topologica…

[Phys. Rev. B 108, 214104] Published Thu Dec 14, 2023

Impact of hyperfine contributions on the ground state of spin-ice compounds
J. Gronemann, S. Chattopadhyay, T. Gottschall, E. Osmic, A. T. M. N. Islam, V. K. Anand, B. Lake, H. Kaneko, H. Suzuki, J. Wosnitza, and T. Herrmannsdörfer
Author(s): J. Gronemann, S. Chattopadhyay, T. Gottschall, E. Osmic, A. T. M. N. Islam, V. K. Anand, B. Lake, H. Kaneko, H. Suzuki, J. Wosnitza, and T. Herrmannsdörfer

Here, the authors determine thermodynamic properties of pyrochlore spin-ice compounds at subkelvin temperatures. In particular, the magnetic field dependence of the heat capacity and magnetic entropy of Ho2Ti2O7 and Pr2Hf2O7 shows the existence of additional states beyond the electronic spin and orbital degrees of freedom. One can understand the data through the presence of hyperfine states and complex hyperfine-coupled term schemes.

[Phys. Rev. B 108, 214412] Published Thu Dec 14, 2023

First-principles study of large gyrotropy in MnBi for infrared thermal photonics
Md Roknuzzaman, Sathwik Bharadwaj, Yifan Wang, Chinmay Khandekar, Dan Jiao, Rajib Rahman, and Zubin Jacob
Author(s): Md Roknuzzaman, Sathwik Bharadwaj, Yifan Wang, Chinmay Khandekar, Dan Jiao, Rajib Rahman, and Zubin Jacob

Nonreciprocal gyrotropic materials have attracted significant interest recently in material physics, nanophotonics, and topological physics. Most of the well-known nonreciprocal materials, however, only show nonreciprocity under a strong external magnetic field and within a small segment of the elec…

[Phys. Rev. B 108, 224307] Published Thu Dec 14, 2023

Magnon currents excited by the spin Seebeck effect in ferromagnetic EuS thin films
M. Xochitl Aguilar-Pujol, Sara Catalano, Carmen González-Orellana, Witold Skowroński, Juan M. Gomez-Perez, Maxim Ilyn, Celia Rogero, Marco Gobbi, Luis E. Hueso, and Fèlix Casanova
Author(s): M. Xochitl Aguilar-Pujol, Sara Catalano, Carmen González-Orellana, Witold Skowroński, Juan M. Gomez-Perez, Maxim Ilyn, Celia Rogero, Marco Gobbi, Luis E. Hueso, and Fèlix Casanova

A magnetic insulator is an ideal platform to propagate spin information by exploiting magnon currents. However, until now, most studies have focused on ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (YIG) and a few other ferri- and antiferromagnetic insulators, but not on pure ferromagnets. In…

[Phys. Rev. B 108, 224420] Published Thu Dec 14, 2023

Anomalous scaling corrections and quantum phase diagram of the Heisenberg antiferromagnet on the spatially anisotropic honeycomb lattice
Alexander Sushchyev and Stefan Wessel
Author(s): Alexander Sushchyev and Stefan Wessel

Using large-scale quantum Monte Carlo simulations, we determine the ground state phase diagram of the spin-1/2 antiferromagnetic Heisenberg model on the honeycomb lattice for the most generic case of three varying interaction strengths along the different lattice directions. We identify continuous q…

[Phys. Rev. B 108, 235146] Published Thu Dec 14, 2023

Intrinsic chiral topological superconductor thin films
Xi Luo, Yu-Ge Chen, Ziqiang Wang, and Yue Yu
Author(s): Xi Luo, Yu-Ge Chen, Ziqiang Wang, and Yue Yu

Superconductors (SCs) with nontrivial topological band structures in the normal state have been discovered recently in bulk materials. When such SCs are made into thin films, quantum tunneling and Cooper pairing take place between the topological surface states (TSSs) on the opposing surfaces. Here,…

[Phys. Rev. B 108, 235147] Published Thu Dec 14, 2023

Kagome and honeycomb flat bands in moiré graphene
Michael G. Scheer and Biao Lian
Author(s): Michael G. Scheer and Biao Lian

We propose a class of graphene-based moiré systems hosting flat bands on kagome and honeycomb moiré superlattices. These systems are formed by stacking a graphene layer on a 2D substrate with lattice constant approximately $\sqrt{3}$ times that of graphene. When the moiré potentials are induced by a…

[Phys. Rev. B 108, 245136] Published Thu Dec 14, 2023

Optimization strategies developed on NiO for Heisenberg exchange coupling calculations using projector augmented wave based first-principles DFT+U+J
Lórien MacEnulty and David D. O'Regan
Author(s): Lórien MacEnulty and David D. O'Regan

High-performance batteries, heterogeneous catalysts, and next-generation photovoltaics often centrally involve transition metal oxides (TMOs) that undergo charge or spin-state changes. Demand for accurate DFT modeling of TMOs has increased in recent years, driving improved quantification and correct…

[Phys. Rev. B 108, 245137] Published Thu Dec 14, 2023

Surface plasmon transformation on dynamic graphene with a periodic modulation of carrier density
A. V. Shirokova, A. V. Maslov, and M. I. Bakunov
Author(s): A. V. Shirokova, A. V. Maslov, and M. I. Bakunov

We explore the transformation of a surface plasmon on dynamic graphene with a periodic modulation of carrier density. We treat the stages of carrier density increases and decreases by using different constitutive relations, which are adequate to the physical mechanisms of carrier injection and remov…

[Phys. Rev. B 108, 245139] Published Thu Dec 14, 2023

Found 2 papers in prl
Date of feed: Fri, 15 Dec 2023 04:17:03 GMT

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

Tunneling Valley Hall Effect Driven by Tilted Dirac Fermions
Shu-Hui Zhang, Ding-Fu Shao, Zi-An Wang, Jin Yang, Wen Yang, and Evgeny Y. Tsymbal
Author(s): Shu-Hui Zhang, Ding-Fu Shao, Zi-An Wang, Jin Yang, Wen Yang, and Evgeny Y. Tsymbal

Valleytronics is a research field utilizing a valley degree of freedom of electrons for information processing and storage. A strong valley polarization is critical for realistic valleytronic applications. Here, we predict a tunneling valley Hall effect (TVHE) driven by tilted Dirac fermions in all-…

[Phys. Rev. Lett. 131, 246301] Published Thu Dec 14, 2023

Phonon Topology and Winding of Spectral Weight in Graphite
N. D. Andriushin, A. S. Sukhanov, A. N. Korshunov, M. S. Pavlovskii, M. C. Rahn, and S. E. Nikitin
Author(s): N. D. Andriushin, A. S. Sukhanov, A. N. Korshunov, M. S. Pavlovskii, M. C. Rahn, and S. E. Nikitin

The topology of electronic and phonon band structures of graphene is well studied and known to exhibit a Dirac cone at the $K$ point of the Brillouin zone. Here, we applied inelastic x-ray scattering (IXS) along with ab initio calculations to investigate phonon topology in graphite, the 3D analog of…

[Phys. Rev. Lett. 131, 246601] Published Thu Dec 14, 2023

Found 1 papers in prx
Date of feed: Fri, 15 Dec 2023 04:17:04 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)

Ultrafast Measurements of Mode-Specific Deformation Potentials of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$ and ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$
Yijing Huang et al.
Author(s): Yijing Huang et al.

Combining two ultrafast spectroscopy techniques allows for measurements of the electron-phonon coupling in two prototypical topological materials.

[Phys. Rev. X 13, 041050] Published Thu Dec 14, 2023

Found 1 papers in pr_res
Date of feed: Fri, 15 Dec 2023 04:17:03 GMT

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

Zeroth, first, and second-order phase transitions in deep neural networks
Liu Ziyin and Masahito Ueda
Author(s): Liu Ziyin and Masahito Ueda

We investigate deep-learning-unique first-order and second-order phase transitions, whose phenomenology closely follows that in statistical physics. In particular, we prove that the competition between prediction error and model complexity in the training loss leads to the second-order phase transit…

[Phys. Rev. Research 5, 043243] Published Thu Dec 14, 2023