Found 58 papers in cond-mat
Date of feed: Tue, 25 Jul 2023 00:30:00 GMT

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Fragmented superconductivity in the Hubbard model as solitons in Ginzburg-Landau theory. (arXiv:2307.11820v1 [cond-mat.str-el])
Niccolò Baldelli, Benedikt Kloss, Matthew Fishman, Alexander Wietek

The phenomena of superconductivity and charge density waves are observed in close vicinity in many strongly correlated materials. Increasing evidence from experiments and numerical simulations suggests both phenomena can also occur in an intertwined manner, where the superconducting order parameter is coupled to the electronic density. Employing density matrix renormalization group simulations, we investigate the nature of such an intertwined state of matter stabilized in the phase diagram of the elementary $t$-$t^\prime$-$U$ Hubbard model in the strong coupling regime. Remarkably, the condensate of Cooper pairs is shown to be fragmented in the presence of a charge density wave where more than one pairing wave function is macroscopically occupied. Moreover, we provide conclusive evidence that the macroscopic wave functions of the superconducting fragments are well-described by soliton solutions of a Ginzburg-Landau equation in a periodic potential constituted by the charge density wave. In the presence of an orbital magnetic field, the order parameters are gauge invariant, and superconducting vortices are pinned between the stripes. This intertwined Ginzburg-Landau theory is proposed as an effective low-energy description of the stripe fragmented superconductor.

First-principles Calculations of MoSeTe/WSeTe Bilayers: Stability, Phonons, Electronic Band Offsets, and Rashba Splitting. (arXiv:2307.11839v1 [cond-mat.mtrl-sci])
Hamid Mehdipour, Peter Kratzer

Janus materials have attracted much interest due to their intrinsic electric dipole moment which, among other consequences, triggers Rashba band splitting. We show that, by building bilayers of MoSeTe and WSeTe with different chalcogen atom sequences and different stacking patterns, one can modulate the net dipole moment strength and thus the Rashba effect, as well as the band alignment of the MoSeTe/WSeTe bilayer. Type-II band alignment is found which can be exploited to create long-lived interlayer excitons. Moreover, it is shown that the atomic sequence and stacking play pivotal roles in the interlayer distance of MoSeTe/WSeTe and thus its electronic structure and vibrational, especially low-frequency, characteristics. The long-range dispersion forces between atoms are treated with a conventional additive pairwise, as well as a many-body-dispersion method. It is shown that under the many-body dispersion method, more clear and rational thermodynamic trends of bilayer stacking are realized and interface distances are estimated more accurately. Vibrational spectra of the bilayers are calculated using first-principles phonon calculations and the fingerprints of monolayer attraction and repulsion are identified. An anti-correlation between distance and the shearing mode frequency of the rigid monolayers is demonstrated which agrees well with experimental findings. The results suggest that the judicious selection of the atomic sequence and stacking helps to widen the scope of the low-dimensional materials by adding or enhancing properties for specific applications, e.g. for spintronics or valleytronics devices.

Higher-order Topological Point State. (arXiv:2307.11890v1 [cond-mat.mtrl-sci])
Xiaoyin Li, Feng Liu

Higher-order topological insulators (HOTIs) have attracted increasing interest as a unique class of topological quantum materials. One distinct property of HOTIs is the crystalline symmetry-imposed topological state at the lower-dimensional outer boundary, e.g. the zero-dimensional (0D) corner state of a 2D HOTI, used exclusively as a universal signature to identify higher-order topology but yet with uncertainty. Strikingly, we discover the existence of inner topological point states (TPS) in a 2D HOTI, as the embedded "end" states of 1D first-order TI, as exemplified by those located at the vacancies in a Kekule lattice. Significantly, we demonstrate that such inner TPS can be unambiguously distinguished from the trivial point-defect states, by their unique topology-endowed inter-TPS interaction and correlated magnetic response in spectroscopy measurements, overcoming an outstanding experimental challenge. Furthermore, based on first-principles calculations, we propose {\gamma}-graphyne as a promising material to observe the higher-order TPS. Our findings shed new light on our fundamental understanding of HOTIs, and also open an avenue to experimentally distinguishing and tuning TPS in the interior of a 2D sample for potential applications.

Magnetism and topological property in icosahedral quasicrystal. (arXiv:2307.11898v1 [cond-mat.str-el])
Shinji Watanabe

Quasicrystal (QC) has no periodicity but has a unique rotational symmetry forbidden in periodic crystals. Lack of microscopic theory of the crystalline electric field (CEF) in the QC and approximant crystal (AC) has prevented us from understanding the electric property, especially the magnetism. By developing the general formulation of the CEF in the rare-earth based QC and AC, we have analyzed the CEF in the QC Au-SM-Tb and AC (SM=Si, Ge, and Ga). The magnetic anisotropy arising from the CEF plays an important role in realizing unique magnetic states on the icosahedron (IC). By constructing the minimal model with the magnetic anisotropy, we have analyzed the ground-state properties of the IC, 1/1 AC, and QC. The hedgehog state is characterized by the topological charge of one and the whirling-moment state is characterized by the topological charge of three. The uniform arrangement of the ferrimagnetic state is stabilized in the QC with the ferromagnetic (FM) interaction, which is a candidate for the magnetic structure recently observed FM long-range order in the QC Au-Ga-Tb. The uniform arrangement of the hedgehog state is stabilized in the QC with the antiferromagnetic interaction, which suggests the possibility of the topological magnetic long-range order.

Light-Driven Nanoscale Vectorial Currents. (arXiv:2307.11928v1 [cond-mat.mes-hall])
Jacob Pettine, Prashant Padmanabhan, Teng Shi, Lauren Gingras, Luke McClintock, Chun-Chieh Chang, Kevin W. C. Kwock, Long Yuan, Yue Huang, John Nogan, Jon K. Baldwin, Peter Adel, Ronald Holzwarth, Abul K. Azad, Filip Ronning, Antoinette J. Taylor, Rohit P. Prasankumar, Shi-Zeng Lin, Hou-Tong Chen

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical manipulation of currents at nanometer spatial scales remains a basic challenge and a key step toward scalable optoelectronic systems and local probes. Here, we introduce vectorial optoelectronic metasurfaces as a new class of metamaterial in which ultrafast charge flows are driven by light pulses, with actively-tunable directionality and arbitrary patterning down to sub-diffractive nanometer scales. In the prototypical metasurfaces studied herein, asymmetric plasmonic nanoantennas locally induce directional, linear current responses within underlying graphene. Nanoscale unit cell symmetries are read out via polarization- and wavelength-sensitive currents and emitted terahertz (THz) radiation. Global vectorial current distributions are revealed by spatial mapping of the THz field polarization, also demonstrating the direct generation of elusive broadband THz vector beams. We show that a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to these currents through rapidly-evolving nanoscale forces and charge flows under extreme spatial and temporal localization. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, nano-magnetism, microelectronics, and ultrafast information science.

Minimal AC injection into Carbon Nanotubes. (arXiv:2307.11943v1 [cond-mat.mes-hall])
Kota Fukuzawa, Takeo Kato, Thibaut Jonckheere, Jérôme Rech, Thierry Martin

We study theoretically the effect of electronic interactions in 1d systems on electron injection using periodic Lorentzian pulses, known as Levitons. We consider specifically a system composed of a metallic single-wall carbon nanotube, described with the Luttinger liquid formalism, a scanning tunneling microscope (STM) tip, and metallic leads. Using the out-of-equilibrium Keldysh Green function formalism, we compute the current and current noise in the system. We prove that the excess noise vanishes when each Leviton injects an integer number of electrons from the STM tip into the nanotube. This extends the concept of minimal injection with Levitons to strongly correlated, uni-dimensional non-chiral systems. We also study the time-dependent current profile, and show how it is the result of interferences between pulses non-trivially reflected at the nanotube/lead interface.

LCPOM: Precise Reconstruction of Polarized Optical Microscopy Images of Liquid Crystals. (arXiv:2307.11944v1 [cond-mat.soft])
Chuqiao Chen, Viviana Palacio-Betancur, Sepideh Norouzi, Pablo F. Zubieta Rico, Monirosadat Sadati, Stuart J. Rowan, Juan J. de Pablo

When viewed with a cross-polarized optical microscope (POM), liquid crystals display interference colors and complex patterns that depend on the material's microscopic orientation. That orientation can be manipulated by application of external fields, which provides the basis for applications in optical display and sensing technologies. The color patterns themselves have a high information content. Traditionally, however, calculations of the optical appearance of liquid crystals have been performed by assuming that a single-wavelength light source is employed, and reported in a monochromatic scale. In this work, the original Jones matrix method is extended to calculate the colored images that arise when a liquid crystal is exposed to a multi-wavelength source. By accounting for the material properties, the visible light spectrum and the CIE color matching functions, we demonstrate that the proposed approach produces colored POM images that are in quantitative agreement with experimental data. Results are presented for a variety of systems, including radial, bipolar, and cholesteric droplets, where results of simulations are compared to experimental microscopy images. The effects of droplet size, topological defect structure, and droplet orientation are examined systematically. The technique introduced here generates images that can be directly compared to experiments, thereby facilitating machine learning efforts aimed at interpreting LC microscopy images, and paving the way for the inverse design of materials capable of producing specific internal microstructures in response to external stimuli.

The mechanical response of fire ant rafts. (arXiv:2307.11966v1 [cond-mat.soft])
Robert J. Wagner, Samuel Lamont, Zachary T. White, Franck J. Vernerey

Fire ants (Solenopsis invicta) cohesively aggregate via the formation of voluntary ant-to-ant attachments when under confinement or exposed to water. Once formed, these aggregations act as viscoelastic solids due to dynamic bond exchange between neighboring ants as demonstrated by rate-dependent mechanical response of 3D aggregations, confined in rheometers. We here investigate the mechanical response of 2D, planar ant rafts roughly as they form in nature. Specifically, we load rafts under uniaxial tension to failure, as well as to 50% strain for two cycles with various recovery times between. We do so while measuring raft reaction force (to estimate network-scale stress), as well as the networks' instantaneous velocity fields and topological damage responses to elucidate the ant-scale origins of global mechanics. The rafts display brittle-like behavior even at slow strain rates (relative to the unloaded bond detachment rate) for which Transient Network Theory predicts steady-state creep. This provides evidence that loaded ant-to-ant bonds undergo mechanosensitive bond stabilization or act as \say{catch bonds}. This is further supported by the coalescence of voids that nucleate due to biaxial stress conditions and merge due to bond dissociation. The characteristic timescales of void coalescence due to chain dissociation provide evidence that the local detachment of stretched bonds is predominantly strain- (as opposed to bond lifetime-) dependent, even at slow strain rates, implying that bond detachment rates diminish significantly under stretch. Significantly, when the voids are closed by restoring the rafts to unstressed conditions, mechanical recovery occurs, confirming the presence of concentration-dependent bond association that - combined with force-diminished dissociation - could further bolster network cohesion under certain stress states.

Imaging Josephson Vortices on Curved Junctions. (arXiv:2307.11970v1 [cond-mat.supr-con])
Yuita Fujisawa, Anjana Krishnadas, Barnaby R.M. Smith, Markel Pardo-Almanza, Hoshu Hiyane, Yuki Nagai, Tadashi Machida, Yoshinori Okada

Understanding the nature of vortices in type-II superconductors has been vital for deepening the physics of exotic superconductors and applying superconducting materials to future electronic devices. A recent study has shown that the LiTi2O4(111) thin film offers a unique experimental platform to unveil the nature of the vortex along the curved Josephson junction. This study successfully visualized individual Josephson vortices along the curved Josephson junctions using in-situ spectroscopic scanning tunneling microscopy on LiTi2O4 (111) epitaxial thin films. Notably, the local curvature of the Josephson junction was discovered to control the position of Josephson vortices. Furthermore, the numerical simulation reproduces the critical role of the curvature of the Josephson junction. This study provides guidelines to control Josephson vortices through geometrical ways, such as mechanical controlling of superconducting materials and their devices.

Unconventional quantum criticality in a non-Hermitian extended Kitaev chain. (arXiv:2307.11996v1 [cond-mat.str-el])
S Rahul, Nilanjan Roy, Ranjith R Kumar, Y R Kartik, Sujit Sarkar

We investigate the nature of quantum criticality and topological phase transitions near the critical lines obtained for the extended Kitaev chain with next nearest neighbor hopping parameters and non-Hermitian chemical potential. We surprisingly find multiple gap-less points, the locations of which in the momentum space can change along the critical line unlike the Hermitian counterpart. The interesting simultaneous occurrences of vanishing and sign flipping behavior by real and imaginary components, respectively of the lowest excitation is observed near the topological phase transition. Introduction of non- Hermitian factor leads to an isolated critical point instead of a critical line and hence, reduced number of multi-critical points as compared to the Hermitian case. The critical exponents obtained for the multi-critical and critical points show a very distinct behavior from the Hermitian case.

The Firs Room-Temperature Ambient-Pressure Superconductor. (arXiv:2307.12008v1 [cond-mat.supr-con])
Sukbae Lee, Ji-Hoon Kim, Young-Wan Kwon

For the first time in the world, we succeeded in synthesizing the room-temperature superconductor (Tc above 400 K, 127 oC) working at ambient pressure with a modified lead-apatite (LK-99) structure. The superconductivity of LK-99 is proved with the Critical temperature (Tc), Zero-resistivity, Critical current (Ic), Critical magnetic field (Hc), and the Meissner effect. The superconductivity of LK-99 originates from minute structural distortion by a slight volume shrinkage (0.48 %), not by external factors such as temperature and pressure. The shrinkage is caused by Cu2+ substitution of Pb2+(2) ions in the insulating network of Pb(2)-phosphate and it generates the stress. It concurrently transfers to Pb(1) of the cylindrical column resulting in distortion of the cylindrical column interface, which creates superconducting quantum wells (SQWs) in the interface. The heat capacity results indicated that the new model is suitable for explaining the superconductivity of LK-99. The unique structure of LK-99 that allows the minute distorted structure to be maintained in the interfaces is the most important factor that LK-99 maintains and exhibits superconductivity at room temperatures and ambient pressure.

Superconductor Pb_{10-x}Cu_x(PO_4)_6O showing levitation at room temperature and atmospheric pressure and mechanism. (arXiv:2307.12037v1 [cond-mat.supr-con])
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 at (0.9<x<1.1), has been synthesized using the solid-state method. The material exhibits the Ohmic metal characteristic of Pb(6s^1) above its superconducting critical temperature, Tc, and the levitation phenomenon as Meissner effect of a superconductor at room temperature and atmospheric pressure below Tc. A LK-99 sample shows Tc above 126.85C (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 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.

Quasi-bound Electron Pairs in Two-Dimensional Materials with a Mexican-Hat Dispersion. (arXiv:2307.12076v1 [cond-mat.str-el])
Vladimir A. Sablikov, Aleksei A. Sukhanov

We study quasi-bound states of two electrons that arise in two-dimensional materials with a Mexican-hat dispersion (MHD) at an energy above its central maximum. The width of the resonance of the local density of states created by pairs is determined by the hybridization of atomic orbitals, due to which the MHD is formed. The mechanism of the quasi-bound state formation is due to the fact that effective reduced mass of electrons near the MHD top is negative. An unusual feature of quasi-bound states is that the resonance width can vanish and then they transform into bound states in continuum. We study in detail the quasi-bound states for topological insulators, when the MHD is due to the hybridization of inverted electron and hole bands. In this case, the resonance width is extremely small at weak hybridization. The highest binding energy is achieved for singlet quasi-bound pairs with zero angular number.

Nonlinear Valley Hall Effect. (arXiv:2307.12088v1 [cond-mat.mes-hall])
Kamal Das, Koushik Ghorai, Dimitrie Culcer, Amit Agarwal

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

Ultrafast measurements of mode-specific deformation potentials of Bi$_2$Te$_3$ and Bi$_2$Se$_3$. (arXiv:2307.12132v1 [cond-mat.mtrl-sci])
Yijing Huang, José D. Querales-Flores, Samuel W. Teitelbaum, Jiang Cao, Thomas Henighan, Hanzhe Liu, Mason Jiang, Gilberto De la Peña, Viktor Krapivin, Johann Haber, Takahiro Sato, Matthieu Chollet, Diling Zhu, Tetsuo Katayama, Robert Power, Meabh Allen, Costel R. Rotundu, Trevor P. Bailey, Ctirad Uher, Mariano Trigo, Patrick S. Kirchmann, Éamonn D. Murray, Zhi-Xun Shen, Ivana Savic, Stephen Fahy, Jonathan A. Sobota, David A. Reis

Quantifying electron-phonon interactions for the surface states of topological materials can provide key insights into surface-state transport, topological superconductivity, and potentially how to manipulate the surface state using a structural degree of freedom. We perform time-resolved x-ray diffraction (XRD) and angle-resolved photoemission (ARPES) measurements on Bi$_2$Te$_3$ and Bi$_2$Se$_3$, following the excitation of coherent A$_{1g}$ optical phonons. We extract and compare the deformation potentials coupling the surface electronic states to local A$_{1g}$-like displacements in these two materials using the experimentally determined atomic displacements from XRD and electron band shifts from ARPES.We find the coupling in Bi$_2$Te$_3$ and Bi$_2$Se$_3$ to be similar and in general in agreement with expectations from density functional theory. We establish a methodology that quantifies the mode-specific electron-phonon coupling experimentally, allowing detailed comparison to theory. Our results shed light on fundamental processes in topological insulators involving electron-phonon coupling.

Effects of Coulomb blockade on the charge transport through the topological states of finite armchair graphene nanoribbons and heterostructures. (arXiv:2307.12192v1 [cond-mat.mes-hall])
David M T Kuo

In this study, we investigate the charge transport properties of semiconducting armchair graphene nanoribbons (AGNRs) and heterostructures through their topological states (TSs), with a specific focus on the Coulomb blockade region. Our approach employs a two-site Hubbard model that takes into account both intra- and inter-site Coulomb interactions. Using this model, we calculate the electron thermoelectric coefficients and tunneling currents of serially coupled TSs (SCTSs). In the linear response regime, we analyze the electrical conductance ($G_e$), Seebeck coefficient ($S$), and electron thermal conductance ($\kappa_e$) of finite AGNRs. Our results reveal that at low temperatures, the Seebeck coefficient is more sensitive to many-body spectra than the electrical conductance. Furthermore, we observe that the optimized $S$ at high temperature is less sensitive to electron Coulomb interactions than $G_e$ and $\kappa_e$. In the nonlinear response regime, we observe a tunneling current with negative differential conductance through the SCTSs of finite AGNRs. This current is generated by electron inter-site Coulomb interactions rather than intra-site Coulomb interactions. Additionally, we observe current rectification behavior in asymmetrical junction systems of SCTSs of AGNRs. Notably, we also uncover the remarkable current rectification behavior of SCTSs of 9-7-9 AGNR heterostructure in the Pauli spin blockade configuration. Overall, our study provides valuable insights into the charge transport properties of TSs in finite AGNRs and heterostructures. We emphasize the importance of considering electron-electron interactions in understanding the behavior of these materials.

Observation of spin polarons in a frustrated moir\'e Hubbard system. (arXiv:2307.12205v1 [cond-mat.str-el])
Zui Tao, Wenjin Zhao, Bowen Shen, Patrick Knüppel, Kenji Watanabe, Takashi Taniguchi, Jie Shan, Kin Fai Mak

The electron's kinetic energy plays a pivotal role in magnetism. While virtual electron hopping promotes antiferromagnetism in an insulator, the real process usually favors ferromagnetism. But in kinetically frustrated systems, such as hole doped triangular lattice Mott insulators, real hopping has been shown to favor antiferromagnetism. Kinetic frustration has also been predicted to induce a new quasiparticle -- a bound state of the doped hole and a spin flip called a spin polaron -- at intermediate magnetic fields, which could form an unusual metallic state. However, the direct experimental observation of spin polarons has remained elusive. Here we report the observation of spin polarons in triangular lattice MoTe2/WSe2 moir\'e bilayers by the reflective magnetic circular dichroism measurements. We identify a spin polaron phase at lattice filling factor between 0.8-1 and magnetic field between 2-4 T; it is separated from the fully spin polarized phase by a metamagnetic transition. We determine that the spin polaron is a spin-3/2 particle and its binding energy is commensurate to the kinetic hopping energy. Our results open the door for exploring spin polaron pseudogap metals, spin polaron pairing and other new phenomena in triangular lattice moir\'e materials.

Green's Function Zeros in Fermi Surface Symmetric Mass Generation. (arXiv:2307.12223v1 [cond-mat.str-el])
Da-Chuan Lu, Meng Zeng, Yi-Zhuang You

The Fermi surface symmetric mass generation (SMG) is an intrinsically interaction-driven mechanism that opens an excitation gap on the Fermi surface without invoking symmetry-breaking or topological order. We explore this phenomenon within a bilayer square lattice model of spin-1/2 fermions, where the system can be tuned from a metallic Fermi liquid phase to a strongly-interacting SMG insulator phase by an inter-layer spin-spin interaction. The SMG insulator preserves all symmetries and has no mean-field interpretation at the single-particle level. It is characterized by zeros in the fermion Green's function, which encapsulate the same Fermi volume in momentum space as the original Fermi surface, a feature mandated by the Luttinger theorem. Utilizing both numerical and field-theoretical methods, we provide compelling evidence for these Green's function zeros across both strong and weak coupling regimes of the SMG phase. Our findings highlight the robustness of the zero Fermi surface, which offers promising avenues for experimental identification of SMG insulators through spectroscopy experiments despite potential spectral broadening from noise or dissipation.

The electronic structure of intertwined kagome, honeycomb, and triangular sublattices of the intermetallics MCo$_2$Al$_9$. (arXiv:2307.12269v1 [cond-mat.str-el])
Chiara Bigi, Sahar Pakdel, Michał J. Winiarski, Pasquale Orgiani, Ivana Vobornik, Jun Fujii, Giorgio Rossi, Vincent Polewczyk, Phil D.C. King, Giancarlo Panaccione, Tomasz Klimczuk, Kristian Sommer Thygesen, Federico Mazzola

Intermetallics are an important playground to stabilize a large variety of physical phenomena, arising from their complex crystal structure. The ease of their chemical tuneabilty makes them suitable platforms to realize targeted electronic properties starting from the symmetries hidden in their unit cell. Here, we investigate the family of the recently discovered intermetallics MCo$_2$Al$_9$ (M: Sr, Ba) and we unveil their electronic structure for the first time. By using angle-resolved photoelectron spectroscopy and density functional theory calculations, we discover the existence of Dirac-like dispersions as ubiquitous features in this family, coming from the hidden kagome and honeycomb symmetries embedded in the unit cell. Finally, from calculations, we expect that the spin-orbit coupling is responsible for opening energy gaps in the electronic structure spectrum, which also affects the majority of the observed Dirac-like states. Our study constitutes the first experimental observation of the electronic structure of MCo$_2$Al$_9$ and proposes these systems as hosts of Dirac-like physics with intrinsic spin-orbit coupling. The latter effect suggests MCo$_2$Al$_9$ as a future platform for investigating the emergence of non-trivial topology.

Backscattering of topologically protected helical edge states by line defects. (arXiv:2307.12271v1 [cond-mat.mes-hall])
Mohadese Karimi, Mohsen Amini, Morteza Soltani, Mozhgan Sadeghizadeh

The quantization of conductance in the presence of non-magnetic point defects is a consequence of topological protection and the spin-momentum locking of helical edge states in two-dimensional topological insulators. This protection ensures the absence of backscattering of helical edge modes in the quantum Hall phase of the system. However, our study focuses on exploring a novel approach to disrupt this protection. We propose that a linear arrangement of on-site impurities can effectively lift the topological protection of edge states in the Kane-Mele model. To investigate this phenomenon, we consider an armchair ribbon containing a line defect spanning its width. Utilizing the tight-binding model and non-equilibrium Green's function method, we calculate the transmission coefficient of the system. Our results reveal a suppression of conductance at energies near the lower edge of the bulk gap for positive on-site potentials. To further comprehend this behavior, we perform analytical calculations and discuss the formation of an impurity channel. This channel arises due to the overlap of in-gap bound states, linking the bottom edge of the ribbon to its top edge, consequently facilitating backscattering. Our explanation is supported by the analysis of the local density of states at sites near the position of impurities.

Spin-Peierls instability of the U(1) Dirac spin liquid. (arXiv:2307.12295v1 [cond-mat.str-el])
Urban F. P. Seifert, Josef Willsher, Markus Drescher, Frank Pollmann, Johannes Knolle

Quantum spin liquids are tantalizing phases of frustrated quantum magnets. A complicating factor in their realization and observation in materials is the ubiquitous presence of other degrees of freedom, in particular lattice distortion modes (phonons). These provide additional routes for relieving magnetic frustration, thereby possibly destabilizing spin-liquid ground states. In this work, we focus on triangular-lattice Heisenberg antiferromagnets, where recent numerical evidence suggests the presence of an extended U(1) Dirac spin liquid phase which is described by compact quantum electrodynamics in 2+1 dimensions (QED$_3$), featuring gapless spinons and monopoles as gauge excitations. Its low energy theory is believed to flow to a strongly-coupled fixed point with conformal symmetries. Using complementary perturbation theory and scaling arguments, we show that a symmetry-allowed coupling between (classical) finite-wavevector lattice distortions and monopole operators of the U(1) Dirac spin liquid generally induces a spin-Peierls instability towards a (confining) 12-site valence-bond solid state. We support our theoretical analysis with state-of-the-art density matrix renormalization group simulations. Away from the limit of static distortions, we demonstrate that the phonon energy gap establishes a parameter regime where the spin liquid is expected to be stable.

Active fractal networks with stochastic force monopoles and force dipoles unravel subdiffusion of chromosomal loci. (arXiv:2307.12310v1 [cond-mat.soft])
Sadhana Singh, Rony Granek

We study the Rouse-type dynamics of elastic fractal networks with embedded, stochastically driven, active force monopoles and dipoles, that are temporally correlated. We compute, analytically -- using a general theoretical framework -- and via Langevin dynamics simulations, the mean square displacement of a network bead. Following a short-time super-diffusive behavior, force monopoles yield anomalous subdiffusion with an exponent identical to that of the thermal system. Force dipoles do not induce subdiffusion, and result in rotational motion of the whole network -- as found for micro-swimmers -- and network collapses beyond a critical force amplitude. The collapse persists with increasing system size, signifying a true first-order dynamical phase transition. We conclude that the observed identical subdiffusion exponents of chromosomal loci in normal and ATP-depleted cells are attributed to active force monopoles rather than force dipoles.

Quantum geometric-induced third-order nonlinear transport in antiferromagnetic topological insulator MnBi2Te4. (arXiv:2307.12313v1 [cond-mat.mtrl-sci])
Hui Li, Chengping Zhang, Chengjie Zhou, Chen Ma, Xiao Lei, Hongtao He, Baikui Li, K. T. Law, Jiannong Wang

Discovering the nonlinear transport features in antiferromagnets is of fundamental interest in condensed matter physics as it offers a new frontier of the understanding deep connections between multiple degrees of freedom, including magnetic orders, symmetries, and band geometric properties. Antiferromagnetic topological insulator MnBi${_2}$Te${_4}$ has provided a highly tunable platform for experimental explorations due to its rich magnetic structures and striking topological band structures. Here, we experimentally investigate the third-order nonlinear transport properties in bulk MnBi${_2}$Te${_4}$ flakes. The measured third-harmonic longitudinal ($V_{xx}^{3{\omega}}$) and transverse ($V_{xy}^{3{\omega}}$) voltages show intimate connection with magnetic transitions of MnBi${_2}$Te${_4}$ flakes and their magnitudes change abruptly as MnBi${_2}$Te${_4}$ flakes go through magnetic transitions with varying temperature and magnetic fields. In addition, the measured $V_{xx}^{3{\omega}}$ exhibits an even-symmetric feature with changing magnetic field direction and the $V_{xy}^{3{\omega}}$ shows an odd-symmetric property, which are believed to be related to the quantum metric and the emergency of non-zero Berry curvature quadrupole with broken ${PT}$ symmetry and non-degenerate band structures under external magnetic fields, respectively. Our work shows great advances in the understanding of the underlying interactions between multiple geometric quantities.

Continuous unitary transformation approach to the Kondo-Majorana interplay. (arXiv:2307.12356v1 [cond-mat.mes-hall])
Jan Baranski, Magdalena Baranska, Tomasz Zienkiewicz, Justyna Tomaszewska, Konrad Jerzy Kapcia

We analyze a setup composed of a correlated quantum dot (QD) coupled to one metallic lead and one end of topological chain hosting a Majorana zero mode (MZM). In such a hybrid structure, a leakage of the MZM into the region of the QD competes with the Kondo resonance appearing as a consequence of the spin-exchange interactions between the dot and the lead. In the work, we use the nontrivial technique called the continuous unitary transformation (CUT) to analyze this competition. Using the CUT technique, we inspect the influence of the coupling between the QD and the chain on effective exchange interactions and calculate the resultant Kondo temperature.

Unravelling the Mechanics of Knitted Fabrics Through Hierarchical Geometric Representation. (arXiv:2307.12360v1 [cond-mat.soft])
Xiaoxiao Ding, Vanessa Sanchez, Katia Bertoldi, Chris H. Rycroft

Knitting interloops one-dimensional yarns into three-dimensional fabrics that exhibit behaviours beyond their constitutive materials. How extensibility and anisotropy emerge from the hierarchical organization of yarns into knitted fabrics has long been unresolved. We sought to unravel the mechanical roles of tensile mechanics, assembly and dynamics arising from the yarn level on fabric nonlinearity by developing a yarn-based dynamical model. This physically validated model captures the fundamental mechanical response of knitted fabrics, analogous to flexible metamaterials and biological fiber networks due to geometric nonlinearity within such hierarchical systems. We identify the dictating factors of the mechanics of knitted fabrics, highlighting the previously overlooked but critical effect of pre-tension. Fabric anisotropy originates from observed yarn--yarn rearrangements during alignment dynamics and is topology-dependent. This yarn-based model also provides design flexibility of knitted fabrics to embed functionalities by allowing variation in both geometric configuration and material property. Our hierarchical approach to build up a knitted fabrics computationally modernizes an ancient craft and represents a first step towards mechanical programmability of knitted fabrics in wide engineering applications.

Spin Space Group Theory and Unconventional Magnons in Collinear Magnets. (arXiv:2307.12366v1 [cond-mat.mtrl-sci])
Xiaobing Chen, Jun Ren, Jiayu Li, Yuntian Liu, Qihang Liu

Topological magnons have received substantial interest for their potential in both fundamental research and device applications due to their exotic uncharged yet topologically protected boundary modes. However, their understanding has been impeded by the lack of fundamental symmetry descriptions of magnetic materials, of which the spin Hamiltonians are essentially determined by the isotropic Heisenberg interaction. The corresponding magnon band structures allows for more symmetry operations with separated spin and spatial operations, forming spin space groups (SSGs), than the conventional magnetic space groups. Here we developed spin space group (SSG) theory to describe collinear magnetic configurations, identifying all the 1421 collinear SSGs and categorizing them into four types, constructing band representations for these SSGs, and providing a full tabulation of SSGs with exotic nodal topology. Our representation theory perfectly explains the band degeneracies of previous experiments and identifies new magnons beyond magnetic space groups with topological charges, including duodecuple point, octuple nodal line and charge-4 octuple point. With an efficient algorithm that diagnoses topological magnons in collinear magnets, our work offers new pathways to exploring exotic phenomena of magnonic systems, with the potential to advance the next-generation spintronic devices.

Topological transition from nodal to nodeless Zeeman splitting in altermagnets. (arXiv:2307.12380v1 [cond-mat.mes-hall])
Rafael M. Fernandes, Vanuildo S. de Carvalho, Turan Birol, Rodrigo G. Pereira

In an altermagnet, the symmetry that relates configurations with flipped magnetic moments is a rotation. This makes it qualitatively different from a ferromagnet, where no such symmetry exists, or a collinear antiferromagnet, where this symmetry is a lattice translation. In this paper, we investigate the impact of the crystalline environment on the magnetic and electronic properties of an altermagnet. We find that, because each component of the magnetization acquires its own angular dependence, the Zeeman splitting of the bands has symmetry-protected nodal lines residing on mirror planes of the crystal. Upon crossing the Fermi surface, these nodal lines give rise to pinch points that behave as single or double type-II Weyl nodes. We show that an external magnetic field perpendicular to these mirror planes can only move the nodal lines, such that a critical field value is necessary to collapse the nodes and make the Weyl pinch points annihilate. This unveils the topological nature of the transition from a nodal to a nodeless Zeeman splitting of the bands. We also classify the altermagnetic states of common crystallographic point groups in the presence of spin-orbit coupling, revealing that a broad family of magnetic orthorhombic perovskites can realize altermagnetism.

Chiral topological whispering gallery modes formed by gyromagnetic photonic crystals. (arXiv:2307.12495v1 [physics.optics])
Yongqi Chen, Nan Gao, Guodong Zhu, Yurui Fang

We explore a hexagonal cavity that supports chiral topological whispering gallery (CTWG) modes, formed by a gyromagnetic photonic crystal. This mode is a special type of topologically protected optical mode that can propagate in photonic crystals with chiral direction. Finite element method simulations show that discrete edge states exist in the topological band gap due to the coupling of chiral edge states and WG modes. Since the cavity only supports edge state modes with group velocity in only one direction, it can purely generate traveling modes and be immune to interference modes. In addition, we introduced defects and disorder to test the robustness of the cavity, demonstrating that the CTWG modes can be effectively maintained under all types of perturbations. Our topological cavity platform offers useful prototype of robust topological photonic devices. The existence of this mode can have important implications for the design and application of optical devices.

Spin-dependent gain and loss in photonic quantum spin Hall systems. (arXiv:2307.12503v1 [cond-mat.mes-hall])
Tian-Rui Liu, Kai Bai, Jia-Zheng Li, Liang Fang, Duanduan Wan, Meng Xiao

Topological phases are greatly enriched by including non-Hermiticity. While most works focus on the topology of the eigenvalues and eigenstates, how topologically nontrivial non-Hermitian systems behave in dynamics has only drawn limited attention. Here, we consider a breathing honeycomb lattice known to emulate the quantum spin Hall effect and exhibits higher-order corner modes. We find that non-reciprocal intracell couplings introduce gain in one pseudo-spin subspace while loss with the same magnitude in the other. In addition, non-reciprocal intracell couplings can also suppress the spin mixture of the edge modes at the boundaries and delocalize the higher-order corner mode. Our findings deepen the understanding of non-Hermitian topological phases and bring in the spin degree of freedom in manipulating the dynamics in non-Hermitian systems.

Edge Theories for Anyon Condensation Phase Transitions. (arXiv:2307.12509v1 [cond-mat.str-el])
David M. Long, Andrew C. Doherty

The algebraic tools used to study topological phases of matter are not clearly suited to studying processes in which the bulk energy gap closes, such as phase transitions. We describe an elementary two edge thought experiment which reveals the effect of an anyon condensation phase transition on the robust edge properties of a sample, bypassing a limitation of the algebraic description. In particular, the two edge construction allows some edge degrees of freedom to be tracked through the transition, despite the bulk gap closing. The two edge model demonstrates that bulk anyon condensation induces symmetry breaking in the edge model. Further, the construction recovers the expected result that the number of chiral current carrying modes at the edge cannot change through anyon condensation. We illustrate the construction through detailed analysis of anyon condensation transitions in an achiral phase, the toric code, and in chiral phases, the Kitaev spin liquids.

Quantum Geometry and Landau Levels of Quadratic Band Crossing Points. (arXiv:2307.12528v1 [cond-mat.mes-hall])
Junseo Jung, Hyeongmuk Lim, Bohm-Jung Yang

We study the relation between the quantum geometry of wave functions and the Landau level (LL) spectrum of two-band Hamiltonians with a quadratic band crossing point (QBCP) in two-dimensions. By investigating the influence of interband coupling parameters on the wave function geometry of general QBCPs, we demonstrate that the interband coupling parameters can be entirely determined by the projected elliptic image of the wave functions on the Bloch sphere, which can be characterized by three parameters, i.e., the major $d_1$ and minor $d_2$ diameters of the ellipse, and one angular parameter $\phi$ describing the orientation of the ellipse. These parameters govern the geometric properties of the system such as the Berry phase and modified LL spectra. Explicitly, by comparing the LL spectra of two quadratic band models with and without interband couplings, we show that the product of $d_1$ and $d_2$ determines the constant shift in LL energy while their ratio governs the initial LL energies near a QBCP. Also, by examining the influence of the rotation and time-reversal symmetries on the wave function geometry, we construct a minimal continuum model which exhibits various wave function geometries. We calculate the LL spectra of this model and discuss how interband couplings give LL structure for dispersive bands as well as nearly flat bands.

Local topological order and boundary algebras. (arXiv:2307.12552v1 [math-ph])
Corey Jones, Pieter Naaijkens, David Penneys, Daniel Wallick

We introduce a set of axioms for locally topologically ordered quantum spin systems in terms of nets of local ground state projections, and we show they are satisfied by Kitaev's Toric Code and Levin-Wen type models. Then for a locally topologically ordered spin system on $\mathbb{Z}^{k}$, we define a local net of boundary algebras on $\mathbb{Z}^{k-1}$, which gives a new operator algebraic framework for studying topological spin systems. We construct a canonical quantum channel so that states on the boundary quasi-local algebra parameterize bulk-boundary states without reference to a boundary Hamiltonian. As a corollary, we obtain a new proof of a recent result of Ogata [arXiv:2212.09036] that the bulk cone von Neumann algebra in the Toric Code is of type $\rm{II}$, and we show that Levin-Wen models can have cone algebras of type $\rm{III}$. Finally, we argue that the braided tensor category of DHR bimodules for the net of boundary algebras characterizes the bulk topological order in (2+1)D, and can also be used to characterize the topological order of boundary states.

Adaptive active Brownian particles searching for targets of unknown positions. (arXiv:2307.12578v1 [cond-mat.soft])
Harpreet Kaur, Thomas Franosch, Michele Caraglio

Developing behavioral policies designed to efficiently solve target-search problems is a crucial issue both in nature and in the nanotechnology of the 21st century. Here, we characterize the target-search strategies of simple microswimmers in a homogeneous environment containing sparse targets of unknown positions. The microswimmers are capable of controlling their dynamics by switching between Brownian motion and an active Brownian particle and by selecting the time duration of each of the two phases. The specific conduct of a single microswimmer depends on an internal decision-making process determined by a simple neural network associated with the agent itself. Starting from a population of individuals with random behavior, we exploit the genetic algorithm NeuroEvolution of Augmenting Topologies to show how an evolutionary pressure based on the target-search performances of single individuals helps to find the optimal duration of the two different phases. Our findings reveal that the optimal policy strongly depends on the magnitude of the particle's self-propulsion during the active phase and that a broad spectrum of network topology solutions exists, differing in the number of connections and hidden nodes.

Fate of localization in coupled free chain and disordered chain. (arXiv:2307.12631v1 [cond-mat.dis-nn])
Xiaoshui Lin, Ming Gong

It has been widely believed that almost all states in one-dimensional (1d) disordered systems with short-range hopping and uncorrelated random potential are localized. Here, we consider the fate of these localized states by coupling between a disordered chain (with localized states) and a free chain (with extended states), showing that states in the overlapped and un-overlapped regimes exhibit totally different localization behaviors, which is not a phase transition process. In particular, while states in the overlapped regime are localized by resonant coupling, in the un-overlapped regime of the free chain, significant suppression of the localization with a prefactor of $\xi^{-1} \propto t_v^4/\Delta^4$ appeared, where $t_v$ is the inter-chain coupling strength and $\Delta$ is the energy shift between them. This system may exhibit localization lengths that are comparable with the system size even when the potential in the disordered chain is strong. We confirm these results using the transfer matrix method and sparse matrix method for systems $L \sim 10^6 - 10^9$. These findings extend our understanding of localization in low-dimensional disordered systems and provide a concrete example, which may call for much more advanced numerical methods in high-dimensional models.

Vibrational Entropic Stabilization of Layered Chalcogenides: From Ordered Vacancy Compounds to 2D Layers. (arXiv:2307.12640v1 [cond-mat.mtrl-sci])
Roberto Prado-Rivera, Daniela Radu, Vincent H. Crespi, Yuanxi Wang

Despite the rapid pace of computationally and experimentally discovering new two-dimensional layered materials, a general criteria for a given compound to prefer a layered structure over a non-layered one remains unclear. Articulating such criteria would allow one to identify materials at the verge of an inter-dimensional structural phase transition between a 2D layered phase and 3D bulk one, with potential applications in phase change memory devices. Here we identify a general stabilization effect driven by vibrational entropy that can favor 2D layered structures over 3D bulk structures at higher temperatures, which can manifest in ordered vacancy compounds where phase competition is tight. We demonstrate this vibrational-entropy stabilization effect for three prototypical ordered vacancy chalcogenides, ZnIn2S4 and In2S3, and Cu3VSe4, either by vacancy rearrangement or by cleaving through existing vacancies. The relative vibrational entropy advantage of the 2D layered phase originates mainly from softened out-of-plane dilation phonon modes.

Biaxial strain tuning of exciton energy and polarization in monolayer WS2. (arXiv:2307.12663v1 [cond-mat.mtrl-sci])
G. Kourmoulakis, A. Michail, I. Paradisanos, X. Marie, M.M. Glazov, B. Jorissen, L. Covaci, E. Stratakis, K. Papagelis, J. Parthenios, G. Kioseoglou

We perform micro-photoluminescence and Raman experiments to examine the impact of biaxial tensile strain on the optical properties of WS2 monolayers. A strong shift on the order of -130 meV per % of strain is observed in the neutral exciton emission at room temperature. Under near-resonant excitation we measure a monotonic decrease in the circular polarization degree under applied strain. We experimentally separate the effect of the strain-induced energy detuning and evaluate the pure effect coming from biaxial strain. The analysis shows that the suppression of the circular polarization degree under biaxial strain is related to an interplay of energy and polarization relaxation channels as well as to variations in the exciton oscillator strength affecting the long-range exchange interaction.

Harmonic to anharmonic tuning of moir\'e potential leading to unconventional Stark effect and giant dipolar repulsion in WS$_2$/WSe$_2$ heterobilayer. (arXiv:2307.12880v1 [cond-mat.mes-hall])
Suman Chatterjee, Medha Dandu, Pushkar Dasika, Rabindra Biswas, Sarthak Das, Kenji Watanabe, Takashi Taniguchi, Varun Raghunathan, Kausik Majumdar

Excitonic states trapped in harmonic moir\'e wells of twisted heterobilayers is an intriguing testbed. However, the moir\'e potential is primarily governed by the twist angle, and its dynamic tuning remains a challenge. Here we demonstrate anharmonic tuning of moir\'e potential in a WS$_2$/WSe$_2$ heterobilayer through gate voltage and optical power. A gate voltage can result in a local in-plane perturbing field with odd parity around the high-symmetry points. This allows us to simultaneously observe the first (linear) and second (parabolic) order Stark shift for the ground state and first excited state, respectively, of the moir\'e trapped exciton - an effect opposite to conventional quantum-confined Stark shift. Depending on the degree of confinement, these excitons exhibit up to twenty-fold gate-tunability in the lifetime ($100$ to $5$ ns). Also, exciton localization dependent dipolar repulsion leads to an optical power-induced blueshift of $\sim$1 meV/$\mu$W - a five-fold enhancement over previous reports.

Intruder in a two-dimensional granular system: statics and dynamics of force networks in an experimental system experiencing stick-slip dynamics. (arXiv:2307.12890v1 [cond-mat.soft])
R. Basak, R. Kozlowski, L.A. Pugnaloni, M. Kramar, E.S. Socolar, C.M. Carlevaro, L. Kondic

In quasi-two-dimensional experiments with photoelastic particles confined to an annular region, an intruder constrained to move in a circular path halfway between the annular walls experiences stick-slip dynamics. We discuss the response of the granular medium to the driven intruder, focusing on the evolution of the force network during sticking periods. Because the available experimental data does not include precise information about individual contact forces, we use an approach developed in our previous work (Basak et al, J. Eng. Mechanics (2021)) based on networks constructed from measurements of the integrated strain magnitude on each particle. These networks are analyzed using topological measures based on persistence diagrams, revealing that force networks evolve smoothly but in a nontrivial manner throughout each sticking period, even though the intruder and granular particles are stationary. Characteristic features of persistence diagrams show identifiable changes as a slip is approaching, indicating the existence of slip precursors. Key features of the dynamics are similar for granular materials composed of disks or pentagons, but some details are consistently different. In particular, we find significantly larger fluctuations of the measures computed based on persistence diagrams, and therefore of the underlying networks, for systems of pentagonal particles.

Quantum Duality in Electromagnetism and the Fine-Structure Constant. (arXiv:2307.12927v1 [hep-th])
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.

Competing mechanisms govern the thermal rectification behavior in semi-stochastic polycrystalline graphene with graded grain-density distribution. (arXiv:2307.12940v1 [cond-mat.mtrl-sci])
Simanta Lahkar, Raghavan Ranganathan

Thermal rectifiers are devices that have different thermal conductivities in opposing directions of heat flow. The realization of practical thermal rectifiers relies significantly on a sound understanding of the underlying mechanisms of asymmetric heat transport, and two-dimensional materials offer a promising opportunity in this regard owing to their simplistic structures together with a vast possibility of tunable imperfections. However, the in-plane thermal rectification mechanisms in 2D materials like graphene having directional gradients of grain sizes have remained elusive. In fact, understanding the heat transport mechanisms in polycrystalline graphene, which are more practical to synthesize than large-scale single-crystal graphene, could potentially allow a unique opportunity to combine with other defects and designs for effective optimization of the thermal rectification property. In this work, we investigated the thermal rectification behavior in periodic atomistic models of polycrystalline graphene whose grain arrangements were generated semi-stochastically in order to have different gradient grain-density distributions along the in-plane heat flow direction. We employed the centroid Voronoi tessellation technique to generate realistic grain boundary structures for graphene, and the non-equilibrium molecular dynamics simulations method was used to calculate the thermal conductivities and thermal rectification values. Additionally, detailed phonon characteristics and propagating phonon spatial energy densities were analyzed based on the fluctuation-dissipation theory to elucidate the competitive interplay between two underlying mechanisms that determine the degree of asymmetric heat flow in graded polycrystalline graphene.

Collective epithelial migration is mediated by the unbinding of hexatic defects. (arXiv:2307.12956v1 [cond-mat.soft])
Dimitrios Krommydas, Livio Nicola Carenza, Luca Giomi

Collective cell migration in epithelia relies on cell intercalation: i.e. a local remodelling of the cellular network that allows neighbouring cells to swap their positions. While in common with foams and other passive cellular fluids, intercalation in epithelia crucially depends on active processes, where the local geometry of the network and the contractile forces generated therein conspire to produce an ``avalanche'' of remodelling events, which collectively give rise to a vortical flow at the mesoscopic length scale. In this article we formulate a continuum theory of the mechanism driving this process, built upon recent advances towards understanding the hexatic (i.e. $6-$fold ordered) structure of epithelial layers. Using a combination of active hydrodynamics and cell-resolved numerical simulations, we demonstrate that cell intercalation takes place via the unbinding of topological defects, naturally initiated by fluctuations and whose late-times dynamics is governed by the interplay between passive attractive forces and active self-propulsion. Our approach sheds light on the structure of the cellular forces driving collective migration in epithelia and provides an explanation of the observed extensile activity of in vitro epithelial layers.

Coherent Phonons in Antimony: an Undergraduate Physical Chemistry Solid-State Ultrafast Laser Spectroscopy Experiment. (arXiv:2110.11423v2 [physics.ed-ph] UPDATED)
Ilana J Porter, Michael W. Zuerch, Anne M. Baranger, Stephen R. Leone

Ultrafast laser pump-probe spectroscopy is an important and growing field of physical chemistry that allows the measurement of chemical dynamics on their natural timescales, but undergraduate laboratory courses lack examples of such spectroscopy and the interpretation of the dynamics that occur. Here we develop and implement an ultrafast pump probe spectroscopy experiment for the undergraduate physical chemistry laboratory course at the University of California Berkeley. The goal of the experiment is to expose students to concepts in solid-state chemistry and ultrafast spectroscopy via classic coherent phonon dynamics principles developed by researchers over multiple decades. The experiment utilizes a modern high-repetition-rate 800 nm femtosecond Ti:Sapphire laser, split pulses with a variable time delay, and sensitive detection of transient reflectivity signals using the lock-in technique. The experiment involves minimal intervention from students and is therefore easy and safe to implement in the laboratory. Students first perform an intensity autocorrelation measurement on the femtosecond laser pulses to obtain their temporal duration. Then, students measure the pump-probe reflectivity of a single-crystal antimony sample to determine the period of coherent phonon oscillations initiated by an ultrafast pulse excitation, which is analyzed by fitting to a sine wave. Students who completed the experiment in-person obtained good experimental results, and students who took the course remotely due to the COVID-19 pandemic were provided with the data they would have obtained during the experiment to analyze. Evaluation of student written and oral reports reveals that the learning goals were met, and that students gained an appreciation for the field of ultrafast laser-induced chemistry.

(3+1)D path integral state sums on curved U(1) bundles and U(1) anomalies of (2+1)D topological phases. (arXiv:2111.14827v2 [cond-mat.str-el] UPDATED)
Ryohei Kobayashi, Maissam Barkeshli

Given the algebraic data characterizing any (2+1)D bosonic or fermionic topological order with a global symmetry group $G = \mathrm{U}(1) \rtimes H$, we construct a (3+1)D topologically invariant path integral in the presence of a curved background $G$ gauge field, as an exact combinatorial state sum. Specifically, the $\mathrm{U}(1)$ component of the $G$ gauge field can have a non-trivial second Chern class, extending previous work that was restricted to flat $G$ bundles. Our construction expresses the $\mathrm{U}(1)$ gauge field in terms of a Villain formulation on the triangulation, which includes a 1-form $\mathbb{R}$ gauge field and 2-form $\mathbb{Z}$ gauge field. We develop a new graphical calculus for anyons interacting with "Villain symmetry defects", associated with the 1-form and 2-form background gauge fields. This graphical calculus is used to define the (3+1)D path integral, which can describe either a bosonic or fermionic symmetry-protected topological (SPT) phase. For example, we can construct the topological path integral on curved $\mathrm{U}(1)$ bundles for the (3+1)D fermionic topological insulator in class AII and topological superconductor in class AIII given appropriate (2+1)D fermionic symmetry fractionalization data; these then give invariants of 4-manifolds with Spin$^c$ or Pin$^c$ structures and their generalizations. The (3+1)D path integrals define anomaly indicators for the (2+1)D topological orders; in the case of Abelian (2+1)D topological orders, we derive by explicit computation all of the mixed $\mathrm{U}(1)$ anomaly indicator formulas proposed by Lapa and Levin. We also propose a Spin$^c$ generalization of the Gauss-Milgram sum, valid for super-modular categories.

Electric-magnetic duality of $\mathbb{Z}_2$ symmetry enriched Abelian lattice gauge theory. (arXiv:2201.12361v2 [quant-ph] UPDATED)
Zhian Jia, Dagomir Kaszlikowski, Sheng Tan

Kitaev's quantum double model is a lattice gauge theoretic realization of Dijkgraaf-Witten topological quantum field theory (TQFT), its topologically protected ground state space has broad applications for topological quantum computation and topological quantum memory. We investigate the $\mathbb{Z}_2$ symmetry enriched generalization of the model for the cyclic Abelian group in a categorical framework and present an explicit Hamiltonian construction. This model provides a lattice realization of the $\mathbb{Z}_2$ symmetry enriched topological (SET) phase. We discuss in detail the categorical symmetry of the phase, for which the electric-magnetic (EM) duality symmetry is a special case. The aspects of symmetry defects are investigated using the $G$-crossed unitary braided fusion category (UBFC). By determining the corresponding anyon condensation, the gapped boundaries and boundary-bulk duality are also investigated. Then we carefully construct the explicit lattice realization of EM duality for these SET phases.

Spin-texture topology in curved circuits driven by spin-orbit interactions. (arXiv:2209.11653v3 [cond-mat.mes-hall] UPDATED)
Alberto Hijano, Eusebio J. Rodríguez, Dario Bercioux, Diego Frustaglia

Interferometry is a powerful technique used to extract valuable information about the wave function of a system. In this work, we study the response of spin carriers to the effective field textures developed in curved one-dimensional interferometric circuits subject to the joint action of Rashba and Dresselhaus spin-orbit interactions. By using a quantum network technique, we establish that the interplay between these two non-Abelian fields and the circuit's geometry modify the geometrical characteristics of the spinors, particularly on square circuits, leading to the localisation of the electronic wave function and the suppression of the quantum conductance. We propose a topological interpretation by classifying the corresponding spin textures in terms of winding numbers.

Visualizing and manipulating chiral interface states in a moir\'e quantum anomalous Hall insulator. (arXiv:2212.03380v2 [cond-mat.mes-hall] UPDATED)
Canxun Zhang, Tiancong Zhu, Salman Kahn, Tomohiro Soejima, Kenji Watanabe, Takashi Taniguchi, Alex Zettl, Feng Wang, Michael P. Zaletel, Michael F. Crommie

Moir\'e systems made from stacked two-dimensional materials host novel correlated and topological states that can be electrically controlled via applied gate voltages. We have used this technique to manipulate Chern domains in an interaction-driven quantum anomalous Hall insulator made from twisted monolayer-bilayer graphene (tMBLG). This has allowed the wavefunction of chiral interface states to be directly imaged using a scanning tunneling microscope (STM). To accomplish this tMBLG carrier concentration was tuned to stabilize neighboring domains of opposite Chern number, thus providing topological interfaces completely devoid of any structural boundaries. STM tip pulse-induced quantum dots were utilized to induce new Chern domains and thereby create new chiral interface states with tunable chirality at predetermined locations. Theoretical analysis confirms the chiral nature of observed interface states and enables the determination of the characteristic length scale of valley polarization reversal across neighboring tMBLG Chern domains. tMBLG is shown to be a useful platform for imaging the exotic topological properties of correlated moir\'e systems.

Polaronic and Mott insulating phase of layered magnetic vanadium trihalide VCl3. (arXiv:2301.06501v4 [cond-mat.mtrl-sci] UPDATED)
Dario Mastrippolito, Luigi Camerano, Hanna Swiatek, Břetislav Šmíd, Tomasz Klimczuk, Luca Ottaviano, Gianni Profeta

Two-dimensional (2D) van der Waals (vdW) magnetic $3d$-transition metal trihalides are a new class of functional materials showing exotic physical properties useful for spintronic and memory storage applications. In this article, we report the synthesis and electromagnetic characterization of single-crystalline vanadium trichloride, VCl$_3$, a novel 2D layered vdW Mott insulator, which has a rhombohedral structure (R$\overline{3}$, No. 148) at room temperature. VCl$_3$ undergoes a structural phase transition at 103 K and a subsequent antiferromagnetic transition at 21.8 K. Combining core levels and valence bands x-ray photoemission spectroscopy (XPS) with first-principles density functional theory (DFT) calculations, we demonstrate the Mott Hubbard insulating nature of VCl$_3$ and the existence of electron small 2D magnetic polarons localized on V atom sites by V-Cl bond relaxation. The polarons strongly affect the electromagnetic properties of VCl$_3$ promoting the occupation of dispersion-less spin-polarized V-3d $a_{1g}$ states and band inversion with $e^{'}_{g}$ states. Within the polaronic scenario, it is possible to reconcile different experimental evidences on vanadium trihalides, suggesting that also VI$_3$ hosts polarons. Our results highlight the complex physical behavior of this class of crystals determined by charge trapping, lattice distortions, correlation effects, mixed valence states, and magnetic states.

Demonstration of NV-detected $^{13}$C NMR at 4.2 T. (arXiv:2303.00740v2 [cond-mat.mes-hall] UPDATED)
Yuhang Ren, Cooper Selco, Dylan Kawashiri, Michael Coumans, Benjamin Fortman, Louis S. Bouchard, Karoly Holczer, Susumu Takahashi

The nitrogen-vacancy (NV) center in diamond has enabled studies of nanoscale nuclear magnetic resonance (NMR) and electron paramagnetic resonance with high sensitivity in small sample volumes. Most NV-detected NMR (NV-NMR) experiments are performed at low magnetic fields. While low fields are useful in many applications, high-field NV-NMR with fine spectral resolution, high signal sensitivity, and the capability to observe a wider range of nuclei is advantageous for surface detection, microfluidic, and condensed matter studies aimed at probing micro- and nanoscale features. However, only a handful of experiments above 1 T were reported. Herein, we report $^{13}$C NV-NMR spectroscopy at 4.2 T, where the NV Larmor frequency is 115 GHz. Using an electron-nuclear double resonance technique, we successfully detect NV-NMR of two diamond samples. The analysis of the NMR linewidth based on the dipolar broadening theory of Van Vleck shows that the observed linewidths from sample 1 are consistent with the intrinsic NMR linewidth of the sample. For sample 2 we find a narrower linewidth of 44 ppm. This work paves the way for new applications of nanoscale NV-NMR.

Electrical control of spin and valley in spin-orbit coupled graphene multilayers. (arXiv:2303.04855v2 [cond-mat.str-el] UPDATED)
Taige Wang, Marc Vila, Michael P. Zaletel, Shubhayu Chatterjee

Electrical control of magnetism has been a major techonogical pursuit of the spintronics community, owing to its far-reaching implications for data storage and transmission. Here, we propose and analyze a new mechanism for electrical switching of isospin, using chiral-stacked graphene multilayers, such as bernal bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced spin-orbit coupling from the TMD, we demonstrate electrical switching of correlation-induced spin and/or valley polarization, by reversing a perpendicular displacement field or the chemical potential. We substantiate our proposal with both analytical arguments and self-consistent Hartree-Fock numerics. Finally, we illustrate how the relative alignment of the TMDs, together with the top and bottom gate voltages, can be used to selectively switch distinct isospin flavors, putting forward correlated van der Waals heterostructures as a promising platform for spintronics and valleytronics.

Realizing spin squeezing with Rydberg interactions in a programmable optical clock. (arXiv:2303.08078v2 [quant-ph] UPDATED)
William J. Eckner, Nelson Darkwah Oppong, Alec Cao, Aaron W. Young, William R. Milner, John M. Robinson, Jun Ye, Adam M. Kaufman

Neutral-atom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise single-particle control and detection with a range of tunable entangling interactions. For example, these capabilities have been leveraged for state-of-the-art frequency metrology as well as microscopic studies of entangled many-particle states. In this work, we combine these applications to realize spin squeezing - a widely studied operation for producing metrologically useful entanglement - in an optical atomic clock based on a programmable array of interacting optical qubits. In this first demonstration of Rydberg-mediated squeezing with a neutral-atom optical clock, we generate states that have almost 4 dB of metrological gain. Additionally, we perform a synchronous frequency comparison between independent squeezed states and observe a fractional frequency stability of $1.087(1)\times 10^{-15}$ at one-second averaging time, which is 1.94(1) dB below the standard quantum limit, and reaches a fractional precision at the $10^{-17}$ level during a half-hour measurement. We further leverage the programmable control afforded by optical tweezer arrays to apply local phase shifts in order to explore spin squeezing in measurements that operate beyond the relative coherence time with the optical local oscillator. The realization of this spin-squeezing protocol in a programmable atom-array clock opens the door to a wide range of quantum-information inspired techniques for optimal phase estimation and Heisenberg-limited optical atomic clocks.

Revealing a 3D Fermi Surface Pocket and Electron-Hole Tunneling in UTe$_{2}$ with Quantum Oscillations. (arXiv:2303.09050v2 [cond-mat.str-el] UPDATED)
Christopher Broyles, Zack Rehfuss, Hasan Siddiquee, Jiahui Althena Zhu, Kaiwen Zheng, Martin Nikolo, David Graf, John Singleton, Sheng Ran

Spin triplet superconductor UTe$_{2}$ is widely believed to host a quasi-two-dimensional Fermi surface, revealed by first principal calculations, photoemission and quantum oscillation measurements. An outstanding question still remains as to the existence of a three-dimensional Fermi surface pocket, which is crucial for our understanding of the exotic superconducting and topological properties of UTe$_{2}$. This 3D Fermi surface pocket appears in various theoretical models with different physics origins but has not been detected experimentally. Here for the first time, we provide concrete evidence for a relatively isotropic, small Fermi surface pocket of UTe$_{2}$ via quantum oscillation measurements. In addition, we observed high frequency quantum oscillations corresponding to electron-hole tunneling between adjacent electron and hole pockets. The coexistence of 2D and 3D Fermi surface pockets, as well as the breakdown orbits, provides a test bed for theoretical models and aid the realization of a unified understanding of superconducting state of UTe$_{2}$ from the first-principles approach.

Non-Hermitian Chiral Skin Effect. (arXiv:2304.01422v2 [quant-ph] UPDATED)
Xinran Ma, Kui Cao, Xiaoran Wang, Zheng Wei, Supeng Kou

The interplay between non-Hermitian effects and topological insulators has become a frontier of research in non-Hermitian physics. However, the existence of a non-Hermitian skin effect for topological-protected edge states remains controversial. In this paper, we discover an alternative form of the non-Hermitian skin effect called the non-Hermitian chiral skin effect (NHCSE). NHCSE is a non-Hermitian skin effect under periodic boundary condition rather than open boundary condition. Specifically, the chiral modes of the NHCSE localize around \textquotedblleft topological defects\textquotedblright characterized by global dissipation rather than being confined to the system boundaries. We show its detailed physical properties by taking the non-Hermitian Haldane model as an example. As a result, the intrinsic mechanism of the hybrid skin-topological effect in Chern insulators is fully understood via NHCSE. Therefore, this progress will be helpful for solving the controversial topic of hybrid skin-topological effect and thus benefit the research on both non-Hermitian physics and topological quantum states.

Defect-induced band restructuring and length scales in twisted bilayer graphene. (arXiv:2304.03018v2 [cond-mat.mes-hall] UPDATED)
Lucas Baldo, Tomas Löthman, Patric Holmvall, Annica M. Black-Schaffer

We investigate the effects of single, multiple, and extended defects in the form of non-magnetic impurities and vacancies in twisted bilayer graphene (TBG) at and away from the magic angle, using a fully atomistic model and focusing on the behavior of the flat low-energy moir\'e bands. For strong impurities and vacancies in the $AA$ region we find a complete removal of one of the four moir\'e bands, resulting in a significant depletion of the charge density in the $AA$ regions even at extremely low defect concentrations. We find similar results for other defect locations, with the exception of the least coordinated sites in the $AB$ region, where defects instead result in a peculiar band replacement process within the moir\'e bands. In the vacancy limit, this process yields a band structure misleadingly similar to the pristine case. Moreover, we show that triple point fermions (TPFs), which are the crossing of the Dirac point by a flat band, appearing for single, periodic, defects, are generally not preserved when adding extended or multiple defects, and thus likely not experimentally relevant. We further identify two universal length scales for defects, consisting of charge modulations on the atomic scale and on the moir\'e scale, illustrating the importance of both the atomic and moir\'e structures for understanding TBG. We show that our conclusions hold beyond the magic angle and for fully isolated defects. In summary, our results demonstrate that the normal state of TBG and its moir\'e flat bands are extremely sensitive to both the location and strength of non-magnetic impurities and vacancies, which should have significant implications for any emergent ordered state.

Constrained weak-coupling superconductivity in multiband superconductors. (arXiv:2304.13741v2 [cond-mat.supr-con] UPDATED)
Niels Henrik Aase, Christian Svingen Johnsen, Asle Sudbø

We consider superconductivity in a system with $N$ Fermi surfaces, including intraband and interband effective electron-electron interactions. The effective interaction is described by an $N \times N$ matrix whose elements are assumed to be constant in thin momentum shells around each Fermi surface, giving rise to $s$-wave superconductivity. Starting with attractive intraband interactions in all $N$ bands, we show that too strong interband interactions are detrimental to sustaining $N$ nonzero components of the superconducting order parameter. We find similar results in systems with repulsive intraband interactions. The dimensionality reduction of the order-parameter space is given by the number of nonpositive eigenvalues of the interaction matrix. Using general models and models for superconducting transition metal dichalcogenides and iron pnictides frequently employed in the literature, we show that constraints must be imposed on the order parameter to ensure a lower bound on the free energy and that subsequent higher-order expansions around the global minimum are thermodynamically stable. We also demonstrate that similar considerations are necessary for unconventional pairing symmetries.

Integer and fractional Chern insulators in twisted bilayer MoTe2. (arXiv:2305.00973v3 [cond-mat.mes-hall] UPDATED)
Yihang Zeng, Zhengchao Xia, Kaifei Kang, Jiacheng Zhu, Patrick Knüppel, Chirag Vaswani, Kenji Watanabe, Takashi Taniguchi, Kin Fai Mak, Jie Shan

Chern insulators, which are the lattice analogs of the quantum Hall states, can potentially manifest high-temperature topological orders at zero magnetic field to enable next-generation topological quantum devices. To date, integer Chern insulators have been experimentally demonstrated in several systems at zero magnetic field, but fractional Chern insulators have been reported only in graphene-based systems under a finite magnetic field. The emergence of semiconductor moir\'e materials, which support tunable topological flat bands, opens a new opportunity to realize fractional Chern insulators. Here, we report the observation of both integer and fractional Chern insulators at zero magnetic field in small-angle twisted bilayer MoTe2 by combining the local electronic compressibility and magneto-optical measurements. At hole filling factor {\nu}=1 and 2/3, the system is incompressible and spontaneously breaks time reversal symmetry. We determine the Chern number to be 1 and 2/3 for the {\nu}=1 and {\nu}=2/3 gaps, respectively, from their dispersion in filling factor with applied magnetic field using the Streda formula. We further demonstrate electric-field-tuned topological phase transitions involving the Chern insulators. Our findings pave the way for demonstration of quantized fractional Hall conductance and anyonic excitation and braiding in semiconductor moir\'e materials.

Enhancement of electron magnetic susceptibility due to many-body interactions in monolayer MoSe$_2$. (arXiv:2305.01501v3 [cond-mat.mes-hall] UPDATED)
K. Oreszczuk, A. Rodek, M. Goryca, T. Kazimierczuk, M. Raczynski, J. Howarth, T. Taniguchi, K. Watanabe, M. Potemski, P. Kossacki

Employing the original, all-optical method, we quantify the magnetic susceptibility of a two-dimensional electron gas (2DEG) confined in the MoSe$_2$ monolayer in the range of low and moderate carrier densities. The impact of electron-electron interactions on the 2DEG magnetic susceptibility is found to be particularly strong in the limit of, studied in detail, low carrier densities. Following the existing models, we derive the value of $g_0 = 2.5 \pm 0.4$ for the bare (in the absence of the interaction effects) $g$-factor of the ground state electronic band in the MoSe$_2$ monolayer. The derived value of this parameter is discussed in the context of estimations from other experimental approaches. Surprisingly, the conclusions drawn differ from theoretical ab-initio studies.

Quantum metric nonlinear Hall effect in a topological antiferromagnetic heterostructure. (arXiv:2306.09575v2 [cond-mat.mes-hall] UPDATED)
Anyuan Gao, Yu-Fei Liu, Jian-Xiang Qiu, Barun Ghosh, Thaís V. Trevisan, Yugo Onishi, Chaowei Hu, Tiema Qian, Hung-Ju Tien, Shao-Wen Chen, Mengqi Huang, Damien Bérubé, Houchen Li, Christian Tzschaschel, Thao Dinh, Zhe Sun, Sheng-Chin Ho, Shang-Wei Lien, Bahadur Singh, Kenji Watanabe, Takashi Taniguchi, David C. Bell, Hsin Lin, Tay-Rong Chang, Chunhui Rita Du, Arun Bansil, Liang Fu, Ni Ni, Peter P. Orth, Qiong Ma, Su-Yang Xu

Quantum geometry - the geometry of electron Bloch wavefunctions - is central to modern condensed matter physics. Due to the quantum nature, quantum geometry has two parts, the real part quantum metric and the imaginary part Berry curvature. The studies of Berry curvature have led to countless breakthroughs, ranging from the quantum Hall effect in 2DEGs to the anomalous Hall effect (AHE) in ferromagnets. However, in contrast to Berry curvature, the quantum metric has rarely been explored. Here, we report a new nonlinear Hall effect induced by quantum metric by interfacing even-layered MnBi2Te4 (a PT-symmetric antiferromagnet (AFM)) with black phosphorus. This novel nonlinear Hall effect switches direction upon reversing the AFM spins and exhibits distinct scaling that suggests a non-dissipative nature. Like the AHE brought Berry curvature under the spotlight, our results open the door to discovering quantum metric responses. Moreover, we demonstrate that the AFM can harvest wireless electromagnetic energy via the new nonlinear Hall effect, therefore enabling intriguing applications that bridges nonlinear electronics with AFM spintronics.

Phases of (2+1)D SO(5) non-linear sigma model with a topological term on a sphere: multicritical point and disorder phase. (arXiv:2307.05307v2 [cond-mat.str-el] UPDATED)
Bin-Bin Chen, Xu Zhang, Yuxuan Wang, Kai Sun, Zi Yang Meng

Novel critical phenomena beyond the Landau-Ginzburg-Wilson paradigm have been long sought after. Among many candidate scenarios, the deconfined quantum critical point (DQCP) constitutes the most fascinating one, and its lattice model realization has been debated over the past two decades. Here we apply the spherical Landau level regularization upon the exact (2+1)D SO(5) non-linear sigma model with a topological term to study the potential DQCP therein. Utilizing the state-of-the-art density matrix renormalization group method with explicit $\text{SU(2)}_\text{spin}\times\text{U(1)}_\text{charge}$ symmetries, accompanied by quantum Monte Carlo simulation, we accurately obtain the comprehensive phase diagram of the model on a sphere. We find various novel quantum phases, including a N\'eel state, a ferromagnet (FM), a valence bond solid (VBS) state, a valley polarized (VP) state and quantum disordered phase occupying extended area of the phase diagram. Our results show that two different symmetry-breaking phases, i.e., the SO(2)-breaking VBS and the SO(3)-breaking N\'eel states, are separated by either a weakly first-order transition or the disordered region with a multicritical point in between, thus opening up more interesting questions on this two-decade long debate on the nature of DQCP.

Found 7 papers in prb
Date of feed: Tue, 25 Jul 2023 03:16:59 GMT

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

Optical conductivity signatures of Floquet electronic phases
Andrew Cupo, Joshuah T. Heath, Emilio Cobanera, James D. Whitfield, Chandrasekhar Ramanathan, and Lorenza Viola
Author(s): Andrew Cupo, Joshuah T. Heath, Emilio Cobanera, James D. Whitfield, Chandrasekhar Ramanathan, and Lorenza Viola

Optical conductivity measurements may provide access to distinct signatures of Floquet electronic phases, described theoretically by their quasienergy band structures. In this paper we characterize experimental observables of the Floquet graphene antidot lattice (FGAL), which we introduced previousl…

[Phys. Rev. B 108, 024308] Published Mon Jul 24, 2023

Reversible manipulation of the topological Hall effect by hydrogen
Lin Liu, Zhixiang Ye, Ruilin Zhang, Tao Lin, Mingxia Qiu, Shunpu Li, and Hongyu An
Author(s): Lin Liu, Zhixiang Ye, Ruilin Zhang, Tao Lin, Mingxia Qiu, Shunpu Li, and Hongyu An

We demonstrate that the topological Hall effect (THE) in a $\mathrm{Pd}/{\mathrm{Tm}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ (TmIG) bilayer can be delicately manipulated by ${\mathrm{H}}_{2}$ with a maximum $100%$ tunability in the reversible manner. This phenomenon originates from the variation of …

[Phys. Rev. B 108, 024422] Published Mon Jul 24, 2023

Quantum oscillations in the magnetic Weyl semimetal NdAlSi arising from strong Weyl fermion–$4f$ electron exchange interaction
Jin-Feng Wang, Qing-Xin Dong, Yi-Fei Huang, Zhao-Sheng Wang, Zhao-Peng Guo, Zhi-Jun Wang, Zhi-An Ren, Gang Li, Pei-Jie Sun, Xi Dai, and Gen-Fu Chen
Author(s): Jin-Feng Wang, Qing-Xin Dong, Yi-Fei Huang, Zhao-Sheng Wang, Zhao-Peng Guo, Zhi-Jun Wang, Zhi-An Ren, Gang Li, Pei-Jie Sun, Xi Dai, and Gen-Fu Chen

Magnetic topological materials are a realization of topologically nontrivial electronic band structure with magnetic correlation effects; they offer novel opportunities in manipulating charge/spin transport as well as spin texture. In the search for emergent phenomena that are specific in this class…

[Phys. Rev. B 108, 024423] Published Mon Jul 24, 2023

Topological properties of a periodically driven Creutz ladder
Koustav Roy and Saurabh Basu
Author(s): Koustav Roy and Saurabh Basu

We have investigated a periodically driven Creutz ladder in the presence of two different driving protocols, namely, a sinusoidal drive and a $δ$ kick imparted to the ladder at regular intervals of time. Specifically, we have studied the topological properties corresponding to the trivial and the no…

[Phys. Rev. B 108, 045415] Published Mon Jul 24, 2023

Ultrafast interfacial charge transfer and superior photoelectric conversion properties in one-dimensional Janus-MoSSe/${\mathrm{WSe}}_{2}$ van der Waals heterostructures
Biao Cai, Jianing Tan, Long Zhang, Degao Xu, Jiansheng Dong, and Gang Ouyang
Author(s): Biao Cai, Jianing Tan, Long Zhang, Degao Xu, Jiansheng Dong, and Gang Ouyang

One-dimensional (1D) van der Waals (vdW) heterostructures have attracted great attention due to their excellent photoelectric properties which potentially serve as key components for next-generation optoelectronic devices. However, investigations on the photoelectric conversion properties in 1D vdW …

[Phys. Rev. B 108, 045416] Published Mon Jul 24, 2023

Electronic properties of rhombohedrally stacked bilayer $\mathrm{W}{\mathrm{Se}}_{2}$ obtained by chemical vapor deposition
Aymen Mahmoudi, Meryem Bouaziz, Anis Chiout, Gaia Di Berardino, Nathan Ullberg, Geoffroy Kremer, Pavel Dudin, José Avila, Mathieu Silly, Vincent Derycke, Davide Romanin, Marco Pala, Iann C. Gerber, Julien Chaste, Fabrice Oehler, and Abdelkarim Ouerghi
Author(s): Aymen Mahmoudi, Meryem Bouaziz, Anis Chiout, Gaia Di Berardino, Nathan Ullberg, Geoffroy Kremer, Pavel Dudin, José Avila, Mathieu Silly, Vincent Derycke, Davide Romanin, Marco Pala, Iann C. Gerber, Julien Chaste, Fabrice Oehler, and Abdelkarim Ouerghi

Twisted layers of atomically thin two-dimensional materials support a broad range of quantum materials with engineered optical and transport properties. Transition metal dichalcogenides (TMDs) in the rhombohedral ($3R$, i.e., ${0}^{∘}$ twist) crystal phase have been the focus of significant research…

[Phys. Rev. B 108, 045417] Published Mon Jul 24, 2023

Transport features of a topological superconducting nanowire with a quantum dot: Conductance and noise
Leonel Gruñeiro, Miguel Alvarado, Alfredo Levy Yeyati, and Liliana Arrachea
Author(s): Leonel Gruñeiro, Miguel Alvarado, Alfredo Levy Yeyati, and Liliana Arrachea

We study two-terminal configurations in junctions between a topological superconducting wire with spin-orbit coupling and magnetic field, and an ordinary conductor with an embedded quantum dot. One of the signatures of the Majorana zero modes in the topological phase is a quantization of the zero-bi…

[Phys. Rev. B 108, 045418] Published Mon Jul 24, 2023

Found 1 papers in prl
Date of feed: Tue, 25 Jul 2023 03:16:58 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]+)

Search for Light Dark Matter from the Atmosphere in PandaX-4T
Xuyang Ning et al. (PandaX Collaboration)
Author(s): Xuyang Ning et al. (PandaX Collaboration)

We report a search for light dark matter produced through the cascading decay of $η$ mesons, which are created as a result of inelastic collisions between cosmic rays and Earth’s atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specif…

[Phys. Rev. Lett. 131, 041001] Published Mon Jul 24, 2023

Found 1 papers in pr_res
Date of feed: Tue, 25 Jul 2023 03:16:59 GMT

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

Topological classification of non-Hermitian Hamiltonians with frequency dependence
Maximilian Kotz and Carsten Timm
Author(s): Maximilian Kotz and Carsten Timm

We develop a topological classification of non-Hermitian effective Hamiltonians that depend on momentum and frequency. Such effective Hamiltonians are in one-to-one correspondence to single-particle Green's functions of systems that satisfy translational invariance in space and time but may be inter…

[Phys. Rev. Research 5, 033043] Published Mon Jul 24, 2023