Showing papers in "Physical review in 2023"
TL;DR: In this article , the structural, electronic, dynamical, and optical properties of lutetium hydrides were investigated through thermal and lattice dynamic analysis as well as XRD and superconductor color comparison.
Abstract: Recently, near-ambient superconductivity has been experimentally evidenced in a nitrogen-doped lutetium hydride by Dasenbrock-Gammon \emph{et al.} [Nature 615, 244 (2023)], which yields a remarkable maximum $T_c$ of 294 K at just 10 kbar. However, due to the difficulty of x-ray diffraction (XRD) in identifying light elements such as hydrogen and nitrogen, the crystal structure of the superconductor remains elusive, in particular for the actual stoichiometry of hydrogen and nitrogen and their atomistic positions. This holds even for its parent structure. Here, we set out to address this issue by performing a thorough density functional theory study on the structural, electronic, dynamical, and optical properties of lutetium hydrides. Through thermal and lattice dynamic analysis as well as XRD and superconductor color comparisons, we unambiguously clarified that the parent structures are a mixture of dominant LuH$_2$ phase of the CaF$_2$-type (instead of originally proposed LuH$_3$ structure of $Fm\bar{3}m$ space group) and minor LuH phase of the NaCl-type.
16 citations
TL;DR: In this paper , the authors studied how quantum information and correlations spread under a quantum quench generated by a prototypical non-Hermitian spin chain, using the mapping to fermions to compute the entanglement entropy and the correlation dynamics in the thermodynamic limit.
Abstract: Non-Hermitian quantum many-body systems are attracting widespread interest for their exotic properties, including unconventional quantum criticality and topology. Here we study how quantum information and correlations spread under a quantum quench generated by a prototypical non-Hermitian spin chain. Using the mapping to fermions we solve exactly the problem and compute the entanglement entropy and the correlation dynamics in the thermodynamic limit. Depending on the quench parameters, we identify two dynamical phases. One is characterized by rapidly saturating entanglement and correlations. The other instead presents a logarithmic growth in time, and correlations spreading faster than the Lieb-Robinson bound, with collapses and revivals giving rise to a modulated light-cone structure. Here, in the long-time limit, we compute analytically the entanglement entropy that we show to scale logarithmically with the size of the cut, with an effective central charge that we obtain in closed form. Our results provide an example of an exactly solvable non-Hermitian many-body problem that shows rich physics including entanglement and spectral transitions.
10 citations
TL;DR: In this article , the authors used symmetry analysis and first-principles calculations to discover seven Cs-Te binary systems that have different crystal structures and can host symmetry-enforced topologically nontrivial phonons.
Abstract: In this paper, we used symmetry analyses and first-principles calculations to discover seven Cs-Te binary systems that have different crystal structures and can host symmetry-enforced topologically nontrivial phonons: $P{2}_{1}{2}_{1}{2}_{1}\text{\ensuremath{-}}{\mathrm{Cs}}_{2}\mathrm{Te}, Pbam$-CsTe, $Pnma\text{\ensuremath{-}}{\mathrm{Cs}}_{2}\mathrm{Te}, Pm\overline{3}m$-CsTe, $Cmcm\text{\ensuremath{-}}{\mathrm{Cs}}_{2}{\mathrm{Te}}_{5}, Cmc{2}_{1}\text{\ensuremath{-}}{\mathrm{Cs}}_{2}{\mathrm{Te}}_{3}$, and $P{2}_{1}/c\text{\ensuremath{-}}{\mathrm{CsTe}}_{4}$. These phonons include charge-two Dirac point phonons, charge-one Weyl point phonons, quadratic contact triple point phonons, triple point phonons, butterflylike Weyl nodal line phonons, Dirac nodal line phonons, Weyl nodal loop phonons, multiple straight Weyl nodal line phonons, nodal cage phonons, one-nodal surface phonons, two-nodal surface phonons, and three-nodal surface phonons. Furthermore, the relationship between the crystal structure and the topological properties was thoroughly investigated in this study. More importantly, the Cs-Te binary systems clearly exhibit phononic arc-shaped, phononic nodal-line-shaped, phononic drumheadlike, and phononic torus surface states, which benefit experimental detections. Our theoretical results not only propose various experimentally prepared Cs-Te binary systems with exotic topological phonons and phononic surface states but also explain the structure-property relationship for Cs-Te binary systems based on symmetry analyses.
9 citations
TL;DR: In this article , a hierarchical ordering in lead-based relaxor perovskites with the formula Pb was revealed, where antiphase domains exist, revealing the possible different degree of compositional ordering arising from intralattice ordering.
Abstract: Lead-based relaxor ferroelectric perovskites with the formula $\mathrm{Pb}({\mathrm{B}}_{1/3}{\mathrm{B}}_{2/3}^{\ensuremath{'}}){\mathrm{O}}_{3}$, such as $\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$, can have different degrees of compositional ordering even for the same stoichiometry. Despite intensive investigation, determining the nature of the B and ${\mathrm{B}}^{\ensuremath{'}}$ ordering remains a challenging problem. Here, we reveal a hierarchical ordering in $\mathrm{Pb}({\mathrm{B}}_{1/3}{\mathrm{B}}_{2/3}^{\ensuremath{'}}){\mathrm{O}}_{3}$ on top of the well-known ${\ensuremath{\beta}}^{\text{I}}$ and ${\ensuremath{\beta}}^{\text{II}}$ sublattices, which is the first level of the proposed hierarchy. Such additional ordering, which is found by considering additional nearest neighboring interactions in the model enriches our understanding of the complex nature of the chemical ordering in lead-based ferroelectric relaxors. In addition, we show that $\mathrm{Pb}({\mathrm{Cd}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ has a higher degree of ordering than that of $\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ or $\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ in which antiphase domains exist, revealing the possible different degree of compositional ordering arising from intralattice ordering.
8 citations
TL;DR: In this article , a topological switch for the non-Hermitian skin effect in electrical circuit networks is proposed and experimentally demonstrated, where the operational amplifier and other electric components are controlled by the switch and the nonreciprocal transport of probability for electrical signals is observed when the switch is turned on.
Abstract: Non-Hermitian systems reveal rich physics beyond the Hermitian regime, and have aroused great interest. One remarkable physical phenomenon is the non-Hermitian skin effect. Recently, topological switching for the non-Hermitian skin effect has been theoretically proposed in cold-atom systems. However, experimental realization of such a phenomenon remains a great challenge. Here, we theoretically propose and experimentally demonstrate a topological switch for the non-Hermitian skin effect in electrical circuit networks. By controlling the operational amplifier and other electric components, the nonreciprocal transport of probability for electrical signals is observed when the switch is turned on. Furthermore, the robustness of such a topological switch is demonstrated both theoretically and experimentally when perturbations are added. Our study provides an avenue for controlling electrical signals in circuit networks, with potential applications in the field of integrated circuit design.
8 citations
TL;DR: In this paper , the excited-state variational quantum eigensolver (VQE) was used to probe the many-body localization (MBL) phase of a quantum hardware.
Abstract: Nonequilibrium physics including many-body localization (MBL) has attracted increasing attentions, but theoretical approaches of reliably studying nonequilibrium properties remain quite limited. In this Letter, we propose a systematic approach to probe MBL phases via the excited-state variational quantum eigensolver (VQE) and demonstrate convincing results of MBL on a quantum hardware, which we believe paves a promising way for future simulations of nonequilibrium systems beyond the reach of classical computations in the noisy intermediate-scale quantum (NISQ) era. Moreover, the MBL probing protocol based on excited-state VQE is NISQ-friendly, as it can successfully differentiate the MBL phase from thermal phases with relatively shallow quantum circuits, and it is also robust against the effect of quantum noises.
8 citations
TL;DR: In this paper , the authors presented comprehensive studies of magnetic phases in a series of Janus monolayers (MnAsBr, MnAsI, MnPBr, and MnPCl) via combining first-principles calculations and atomistic spin model simulations and demonstrated that a variety of topological spin textures can be generated by the interplay among complex magnetic interactions.
Abstract: The search for topological magnetism in two-dimensional (2D) magnetic materials is one of the hot topics in spintronics. We present comprehensive studies of magnetic phases in a series of Janus monolayers $\mathrm{Mn}XZ$ (MnAsBr, MnAsI, MnPBr, and MnPCl) and $\mathrm{Cr}YZ$ ($Y=\mathrm{Se}$, Te; and $Z=\mathrm{Cl}$, Br, I) via combining first-principles calculations and atomistic spin model simulations. Sizable Dzyaloshinskii-Moriya interaction can be realized in the $\mathrm{Mn}XZ$ and $\mathrm{Cr}YZ$ monolayers due to their intrinsic inversion symmetry breaking. More interestingly, the $\mathrm{Mn}XZ$ and $\mathrm{Cr}YZ$ monolayers exhibit different degrees of magnetic frustration and isotropic higher-order interactions. Lastly, our atomistic spin model simulations demonstrate that a variety of topological spin textures can be generated by the interplay among complex magnetic interactions. These results provide valuable information and fundamental understanding for topological magnetism in 2D magnets.
7 citations
TL;DR: In this paper , the authors investigated the high-H superconducting (SC) state of UTe2 and found that the SC character is different from that in the low-H SC (LHSC) phase.
Abstract: UTe2 is a recently discovered spin-triplet superconductor. One of the characteristic features of UTe2 is a magnetic field (H)-boosted superconductivity above 16 T when H is applied exactly parallel to the b axis. To date, this superconducting (SC) state has not been thoroughly investigated, and the SC properties as well as the spin state of this high-H SC (HHSC) phase are not well understood. In this study, we performed AC magnetic susceptibility and nuclear magnetic resonance (NMR) measurements and found that, up to 24.8 T, the HHSC state is intrinsic to UTe2 and quite sensitive to the H angle, and that its SC character is different from that in the low-H SC (LHSC) state. The dominant spin component of the spin-triplet pair is along the a axis in the LHSC state but is changed in the HHSC state along the b axis. Our results indicate that H-induced multiple SC states originate from the remaining spin degrees of freedom.
6 citations
TL;DR: In this article , the effects of measurements, performed with a finite density in space, on the ground state of the one-dimensional transverse-field Ising model at criticality are studied.
Abstract: We study the effects of measurements, performed with a finite density in space, on the ground state of the one-dimensional transverse-field Ising model at criticality. Local degrees of freedom in critical states exhibit long-range entanglement, and as a result, local measurements can have highly nonlocal effects. Our analytical investigation of correlations and entanglement in the ensemble of measured states is based on properties of the Ising conformal field theory (CFT), where measurements appear as (1+0)-dimensional defects in the (1+1)-dimensional Euclidean spacetime. So that we can verify our predictions using large-scale free-fermion numerics, we restrict ourselves to parity-symmetric measurements. To describe their averaged effects analytically we use a replica approach, and we show that the defect arising in the replica theory is an irrelevant perturbation to the Ising CFT. Strikingly, the asymptotic scalings of averaged correlations and entanglement entropy are therefore unchanged relative to the ground state. In contrast, the defect generated by postselecting on the most likely measurement outcomes is exactly marginal. We then find that the exponent governing postmeasurement order parameter correlations, as well as the ''effective central charge'' governing the scaling of entanglement entropy, vary continuously with the density of measurements in space. Our work establishes new connections between the effects of measurements on many-body quantum states and of physical defects on low-energy equilibrium properties.
6 citations
TL;DR: In this paper , the thermal transport properties of a-Si were investigated using large-scale molecular dynamics simulations with an accurate and efficient machine-learned neuroevolution potential (NEP) trained against abundant reference data calculated at the quantum-mechanical density-functional-theory level.
Abstract: Amorphous silicon (a-Si) is an important thermal-management material and also serves as an ideal playground for studying heat transport in strongly disordered materials. Theoretical prediction of the thermal conductivity of a-Si in a wide range of temperatures and sample sizes is still a challenge. Herein we present a systematic investigation of the thermal transport properties of a-Si by employing large-scale molecular dynamics (MD) simulations with an accurate and efficient machine-learned neuroevolution potential (NEP) trained against abundant reference data calculated at the quantum-mechanical density-functional-theory level. The high efficiency of NEP allows us to study the effects of finite size and quenching rate in the formation of a-Si in great detail. We find that it requires a simulation cell up to $64,000$ atoms (a cubic cell with a linear size of 11 nm) and a quenching rate down to $10^{11}$ K s$^{-1}$ for fully convergent thermal conductivity. Structural properties, including short- and medium-range order as characterized by the pair correlation function, angular distribution function, coordination number, ring statistics and structure factor are studied to demonstrate the accuracy of NEP and to further evaluate the role of quenching rate. Using both the heterogeneous and the homogeneous nonequilibrium MD methods and the related spectral decomposition techniques, we calculate the temperature- and thickness-dependent thermal conductivity values of a-Si and show that they agree well with available experimental results from 10 K to room temperature. Our results also highlight the importance of quantum effects in the calculated thermal conductivity and support the quantum correction method based on the spectral thermal conductivity.
6 citations
TL;DR: In this paper , the authors presented a systematic and comprehensive theoretical study of Ga vacancy and interstitial migration in monoclinic gallium sesquioxide, based on hybrid functional calculations and the nudged elastic band technique.
Abstract: The authors present a systematic and comprehensive theoretical study of Ga vacancy and interstitial migration in monoclinic gallium sesquioxide, based on hybrid functional calculations and the nudged elastic band technique. Notably, it is shown that the Ga vacancy can form a favorable three-split configuration, consisting of three Ga vacancies and two Ga interstitials, which enables migration with a dramatically lower migration barrier than previously calculated, further demonstrating the important role of split vacancies in this material.
TL;DR: In this paper , a physically motivated modification of a Hamiltonian that generates a variety of multipartite entangled states through the dynamics in the scar subspace has been shown to be useful for phase estimation.
Abstract: Although entanglement is a key resource for quantum-enhanced metrology, not all entanglement is useful. For example, in the process of many-body thermalization, bipartite entanglement grows rapidly, naturally saturating to a volume law. This type of entanglement generation is ubiquitous in nature but has no known application in most quantum technologies. The generation, stabilization, and exploitation of genuine multipartite entanglement, on the other hand, is far more elusive yet highly desirable for metrological applications. Recently, it has been shown that quantum many-body scars can have extensive multipartite entanglement. However, the accessibility of this structure for real application has been so far unclear. In this work, we show how systems containing quantum many-body scars can be used to dynamically generate stable multipartite entanglement and describe how to exploit this structure for phase estimation with a precision that beats the standard quantum limit. Key to this is a physically motivated modification of a Hamiltonian that generates a variety of multipartite entangled states through the dynamics in the scar subspace.
TL;DR: In this paper , the shape of the transition dipole moments is reconstructed using a high-order harmonic spectrum with the band dispersion and the laser field known, and the reconstructed shape shows small variation as the laser parameters, such as intensity, wavelength and pulse duration, are tuned in wide ranges.
Abstract: According to the three-step model for solid high-order harmonic generation, there is a one-to-one correspondence between the emitted photon energy and the band gap where the electron-hole pair is annihilated. In the tunneling excitation regime, as the electron-hole pair is mostly created in the vicinity of the minimum band gap, the conversion efficiency of the high-energy photon should be approximately proportional to the square of the transition dipole moment at the $\mathbf{k}$ point where the high-harmonic photon is emitted. Based on this picture we propose that a high-order harmonic spectrum could be a strong tool to reconstruct the shape of $\mathbf{k}$-dependent transition dipole moments with the band dispersion and the laser field known. Two real systems, e.g., MgO and ZnO, are taken as samples to verify our idea. The reconstructed shape of the transition dipole moments shows small variation as the laser parameters, such as intensity, wavelength, and pulse duration, are tuned in wide ranges, which proves this scheme is robust.
TL;DR: In this article , the first five moments of the dynamic structure factor of the uniform electron gas at the electronic Fermi temperature were obtained based on path integral Monte Carlo simulations, and they were shown to be in agreement with known sum rules for α = 2,4,5.
Abstract: We introduce an exact framework to compute the positive frequency moments $M^{(\alpha)}(\mathbf{q})=\braket{\omega^\alpha}$ of different dynamic properties from imaginary-time quantum Monte Carlo data. As a practical example, we obtain the first five moments of the dynamic structure factor $S(\mathbf{q},\omega)$ of the uniform electron gas at the electronic Fermi temperature based on \emph{ab initio} path integral Monte Carlo simulations. We find excellent agreement with known sum rules for $\alpha=1,3$, and, to our knowledge, present the first results for $\alpha=2,4,5$. Our idea can be straightforwardly generalized to other dynamic properties such as the single-particle spectral function $A(\mathbf{q},\omega)$, and will be useful for a number of applications, including the study of ultracold atoms, exotic warm dense matter, and condensed matter systems.
TL;DR: In this paper , the authors proposed a mechanism to explain why the half quantization is hard to be probed by showing that the half-quantized counterpropagating currents in axion insulator thin films are strongly suppressed due to the hybridization mediated by the massless side-surface states.
Abstract: The axion insulator is believed to host half-quantized chiral currents running antiparallelly on its top and bottom surfaces. However, the experimental detection of the half quantization in axion insulators remains elusive. In this paper, we propose a mechanism to explain why the half quantization is hard to be probed by showing that the half-quantized counterpropagating currents in axion insulator thin films are strongly suppressed due to the hybridization mediated by the massless side-surface states. This side-surface-mediated hybridization leads to a different type of finite-size effect, which features a power-law decay with the increasing film thickness, different from the exponential decay in topological insulators. Moreover, we show that the half quantization can be extracted in the axion insulator phase by adopting the nonlocal transport measurement.
TL;DR: In this paper , the authors show that many-body scars are ubiquitous in quantum link formulations of gauge theories, opening the door to a large venue of models where QMBSs can be explored.
Abstract: Quantum many-body scars (QMBSs) are a paradigm of weak ergodicity breaking with direct technological applications. The authors show that QMBSs are ubiquitous in quantum link formulations of gauge theories, opening the door to a large venue of models where QMBSs can be explored. They demonstrate that QMBSs are not an artifact of these quantum link formulations, rather, they may be an inherent feature of the ideal gauge theory itself.
TL;DR: In this paper , the authors systematically characterize several CO configurations, some proposed for the new member of the family ScV$_6$Sb$_5$ , by combining phenomenological Ginzburg-Landau theories with mean-field analysis.
Abstract: Kagome metals $A$V$_3$Sb$_5$ ($A=$K, Rb, Cs) exhibit an exotic charge order (CO), involving three order parameters, with broken translation and time-reversal symmetries compatible with the presence of orbital currents. The properties of this phase are still intensely debated, and it is unclear if the origin of the CO is mainly due to electron-electron or electron-phonon interactions. Most of the experimental studies confirm the nematicity of this state, a feature that might be enhanced by electronic correlations. However, it is still unclear whether the nematic CO becomes stable at a temperature equal to ($T_{\text{nem}} = T_\text{C}$) or lower than ($T_{\text{nem}}
TL;DR: In this paper , an ab initio Boltzmann transport approach was proposed to evaluate the thermal transport properties of ferromagnetic crystals, and the results showed that phonons dominate the nonelectronic thermal conduction at high temperatures, and magnons may contribute to the thermal conductivity only at low temperatures.
Abstract: We propose an ab initio Boltzmann transport approach taking into account magnon-phonon scattering (MPS) and three-phonon scattering simultaneously to accurately evaluate the thermal transport properties of ferromagnetic crystals. Using this approach, we studied the nonelectronic thermal transport properties of the body-centered cubic iron as a case. The reasonable agreement between our calculation results and the available experimental data suggests that phonons dominate the nonelectronic thermal conduction at high temperatures, and magnons may contribute to the thermal conductivity only at low temperatures. Remarkably, the abnormal increase in the magnon thermal conductivity at high temperatures implies that other magnon-involved scattering events instead of MPS should dominate the magnon thermal conductivity. Moreover, analyses of average scattering rates and heat propagation lengths suggest that hydrodynamic heat transport may occur at low temperatures. This new approach fills the gap in the first-principles evaluation of the coupled magnon-phonon thermal transport properties in magnetic crystals. Our results will provide valuable references for further investigations of the interplay between magnons and phonons and broaden relevant research prospects about heat management and energy manipulation.
TL;DR: In this paper , supercurrent transport measurements in hybrid Josephson junctions comprised of semiconducting InAs nanowires with epitaxial ferromagnetic insulator EuS and superconducting Al coatings were reported.
Abstract: We report supercurrent transport measurements in hybrid Josephson junctions comprised of semiconducting InAs nanowires with epitaxial ferromagnetic insulator EuS and superconducting Al coatings. The wires display a hysteretic superconducting window close to the coercivity, away from zero external magnetic field. Using a multi-interferometer setup, we measure the current-phase relation of multiple magnetic junctions and find an abrupt switch between $\pi$ and 0 phases within the superconducting window. We attribute the 0-$\pi$ transition to the discrete flipping of the EuS domains and provide a qualitative theory showing that a sizable exchange field can polarize the junction and lead to the supercurrent reversal. Both $0$ and $\pi$ phases can be realized at zero external field by demagnetizing the wire.
TL;DR: In this paper , a general procedure for extracting the running coupling constants of the underlying field theory of a given classical statistical model on a two-dimensional lattice, combining tensor network renormalization (TNR) and the finite-size scaling theory of conformal field theory, was proposed.
Abstract: We propose a general procedure for extracting the running coupling constants of the underlying field theory of a given classical statistical model on a two-dimensional lattice, combining tensor network renormalization (TNR) and the finite-size scaling theory of conformal field theory. By tracking the coupling constants at each scale, we are able to visualize the renormalization group (RG) flow and demonstrate it with the classical Ising and 3-state Potts models. Furthermore, utilizing the new methodology, we reveal the limitations due to finite bond dimension D on TNR applied to critical systems. We find that a finite correlation length is imposed by the finite bond dimension in TNR, and it can be attributed to an emergent relevant perturbation that respects the symmetries of the system. The correlation length shows the same power-law dependence on D as the"finite entanglement scaling"of the Matrix Product States.
TL;DR: In this article , it was shown that quantum many-body scars (QMBS) exist in a wide class of lattice gauge theories in one spatial dimension represented by spin-S$ QLMs coupled to dynamical fermions.
Abstract: As a paradigm of weak ergodicity breaking in disorder-free nonintegrable models, quantum many-body scars (QMBS) can offer deep insights into the thermalization dynamics of gauge theories. Having been first discovered in a spin-$1/2$ quantum link formulation of the Schwinger model, it is a fundamental question as to whether QMBS persist for $S>1/2$ since such theories converge to the lattice Schwinger model in the large-$S$ limit, which is the appropriate version of lattice QED in one spatial dimension. In this work, we address this question by exploring QMBS in spin-$S$ $\mathrm{U}(1)$ quantum link models (QLMs) with staggered fermions. We find that QMBS persist at $S>1/2$, with the resonant scarring regime, which occurs for a zero-mass quench, arising from simple high-energy gauge-invariant initial states. We furthermore find evidence of detuned scarring regimes, which occur for finite-mass quenches starting in the physical vacua and the charge-proliferated state. Our results conclusively show that QMBS exist in a wide class of lattice gauge theories in one spatial dimension represented by spin-$S$ QLMs coupled to dynamical fermions.
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TL;DR: In this paper , it was shown that the magnetic order of magnetooptical response is a signature of altermagnetism, which opens intriguing possibility of manufacturing altermagnetic-detwinned samples.
Abstract: MnTe has recently attracted attention as an altermagnetic candidate. Experimentally it has an altermagnetic order of ferromagnetic $ab$ planes, stacked antiferromagnetically along $c$. We show that this magnetic order (by itself non-trivial, since the in-plane exchange in antiferromagnetic) opens intriguing possibility of manufacturing altermagnetically-detwinned samples and generate observable magnetooptical response (which we calculate from first principles) as a signature of altermagnetism.
TL;DR: In this paper , a polarization-dependent bound state in the continuum (BIC) was proposed in a compound grating waveguide structure based on the selectable guided resonance at near-infrared wavelengths.
Abstract: The photonic spin Hall effect (PSHE) plays an important role in both fundamental science and precision metrology. In this paper, we theoretically propose a polarization-dependent bound state in the continuum (BIC) in a compound grating waveguide structure based on the selectable guided resonance at near-infrared wavelengths. Empowered by the unique resonant property and polarization-dependent property of the quasi-BIC, the transverse shift of the PSHE can be intensively enhanced to the order of hundreds of micrometers. Besides, the enhancement of the transverse shift of the PSHE is robust against the geometric parameters. Our work not only provides an all-dielectric platform to achieve giant PSHE, but also offers a viable approach to design high-performance PSHE-based optical devices.
TL;DR: In this paper , the authors proposed a structure with broken inversion and mirror symmetry for two-dimensional (2D) Janus monochalcogenides, inspired by group-III monolayers.
Abstract: Two-dimensional (2D) Janus materials due to their asymmetric structures show fascinating spintronic and piezoelectric properties making them a research hot spot in recent years. In this work, inspired by Janus group-III monochalcogenides, we propose $\mathrm{Zn}AXY$ ($A=\mathrm{Si}$, Ge, Sn, and $X/Y=\mathrm{S}$, Se, Te, $X<Y$) monolayers as a novel structure with broken inversion and mirror symmetry. By calculating cohesive energy and phonon dispersion, eight of nine possible $\mathrm{Zn}AXY$ monolayers are proved to be dynamically stable. In addition, thermal stability of these eight structures is confirmed by ab initio molecular dynamics simulations. The electronic band structures of $\mathrm{Zn}AXY$ monolayers indicate that all of them are indirect semiconductors with strong spin-orbit coupling effects. Lack of inversion symmetry gives rise to Zeeman-type spin splitting at the $K$ point of the conduction band with the highest value of 136 meV for ZnSiSeTe. Furthermore, out-of-plane asymmetry results in Rashba spin splitting (RSS) at the \ensuremath{\Gamma} point of the valence and conduction bands in the most compositions of Janus $\mathrm{Zn}AXY$ monolayers. Among them, ZnGeSTe with ${\ensuremath{\alpha}}_{R}^{{\mathrm{\ensuremath{\Gamma}}}_{V}}$ of $1.79\phantom{\rule{0.28em}{0ex}}\mathrm{eV}\phantom{\rule{0.28em}{0ex}}\AA{}$ and ${\ensuremath{\alpha}}_{R}^{{\mathrm{\ensuremath{\Gamma}}}_{c}}$ of $0.862\phantom{\rule{0.28em}{0ex}}\mathrm{eV}\phantom{\rule{0.28em}{0ex}}\AA{}$ and ZnSiSTe with ${\ensuremath{\alpha}}_{R}^{{\mathrm{\ensuremath{\Gamma}}}_{V}}$ of $1.537\phantom{\rule{0.28em}{0ex}}\mathrm{eV}\phantom{\rule{0.28em}{0ex}}\AA{}$ and ${\ensuremath{\alpha}}_{R}^{{\mathrm{\ensuremath{\Gamma}}}_{c}}$ of $0.756\phantom{\rule{0.28em}{0ex}}\mathrm{eV}\phantom{\rule{0.28em}{0ex}}\AA{}$ are found to be great materials for future spintronic applications. Interestingly, in addition to large RSS, Mexican hat dispersion is observed at the \ensuremath{\Gamma} point of the topmost valence band in these materials. Moreover, the calculated elastic coefficients for the hexagonal $\mathrm{Zn}AXY$ monolayers confirm the mechanical stability of the predicted structures. Finally, Janus $\mathrm{Zn}AXY$ monolayers possess high in-plane (up to 7.46 pm/V) and out-of-plane (up to 0.67 pm/V) piezoelectric coefficients making them appealing alternatives for prevalent piezoelectric materials.
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TL;DR: In this article , the authors propose a solution to solve the problem of the problem: this article ] of "uniformity" and "uncertainty" of the solution.
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TL;DR: In this paper , the electronic properties of two magnetic Weyl semimetal candidates PrAlSi and SmAlSi were studied using angle-resolved photoemission spectroscopy and first-principles calculations.
Abstract: Magnetic topological materials are a class of compounds with the underlying interplay of nontrivial band topology and magnetic spin configuration. Extensive interests have been aroused due to their application potential involved with an array of exotic quantum states. With angle-resolved photoemission spectroscopy and first-principles calculations, here we study the electronic properties of two magnetic Weyl semimetal candidates PrAlSi and SmAlSi. Though the two compounds harbor distinct magnetic ground states (ferromagnetic and antiferromagnetic for PrAlSi and SmAlSi, respectively) and 4 f shell fillings, we find that they share quite anal-ogous low-energy band structure. By the measurements across the magnetic transitions, we further reveal that there is no evident evolution of the band structure in both compounds and the experimental spectra can be well reproduced by the nonmagnetic calculations, together suggesting a negligible e ff ect of the magnetism on their electronic structures and a possibly weak coupling between the localized 4 f electrons and the itinerant conduction electrons. Our results o ff er essential insights into the interactions between magnetism, electron correlations, and topological orders in the R Al X ( R = light rare earth and X = Si or Ge
TL;DR: In this article , the authors predict that the spin/valley isospin magnetism, resembling that seen in moir\'{e} bands, coexists with momentum-polarized phases occurring via a ''flocking transition'' in momentum space.
Abstract: Electron bands in the untwisted bilayer graphene flatten out in a transverse electric field, offering a promising platform for correlated electron physics. We predict that the spin/valley isospin magnetism, resembling that seen in moir\'{e} bands, coexists with momentum-polarized phases occurring via a ``flocking transition'' in momentum space. This transition results in the electron momentum distribution being spontaneously displaced relative to the $K$ and $K'$ valley centers. These phases feature unusual observables such as persistent currents in the ground state. Momentum-polarized carriers ``sample'' the Berry curvature of the conduction band, resulting in a unique behavior of the anomalous Hall conductivity and other effects that do not occur in previously studied systems.
TL;DR: In this article , the authors apply these ideas to intrinsic 2D nodal superconductors, showing a similar degree of control over neutral Dirac quasiparticles, where their velocity is quenched close to a ''magic'' angle, where interactions drive a timereversal breaking phase transition.
Abstract: Stacking 2D materials with a twist has proven to be a successful strategy to realize exotic phases of electrons. Here, the authors apply these ideas to intrinsic 2D nodal superconductors, showing a similar degree of control over neutral Dirac quasiparticles. Their velocity is quenched close to a ``magic'' angle, where interactions drive a time-reversal breaking phase transition. Gating and application of current and magnetic fields are shown to allow tuning their dispersion in future experiments and to open topological gaps.
TL;DR: In this article , the authors show that the nodes of a twisted bilayers can be considered topological defects, and discover antivortices formed in strained moir\'e systems using transmission electron micrographs.
Abstract: Twisted bilayers of two-dimensional materials contain a moir\'e superatomic lattice domain that can be bounded by a domain boundary network. The authors show here that the nodes of this network can be considered topological defects. While the nodes in previously studied twisted moir\'e materials are vortices, the authors discover antivortices formed in strained moir\'e systems using transmission electron micrographs. This work provides insight into the underlying rules governing moir\'e structures, inspiring the construction of new types of moir\'e interfaces.
TL;DR: In this paper , the authors reported the appearance of single-pair multi-Weyl point phonons with the maximum charge number in a cubic crystal structure with the P23$ space group, and the number and charge of the Weyl points and the phononic surface modes can be tuned by applying $1% and $2% uniaxial strains along the [100] and [111] directions, respectively.
Abstract: The realization of multi-Weyl systems with the minimum nonzero number of Weyl points and the maximum charge number remains challenging in topology physics. In this work, based on first-principles calculations, we propose that ${\mathrm{BeH}}_{2}$ is thermodynamically, mechanically, and dynamically stable in a cubic crystal structure with the $P23$ space group. Importantly, this is the first work to report the appearance of single-pair multi-Weyl point phonons with the maximum charge number in $P23$-type ${\mathrm{BeH}}_{2}$. Furthermore, the number and charge of the Weyl points and the phononic surface modes can be tuned by applying $1%$ and $2%$ uniaxial strains along the [100] and [111] directions, respectively. Finally, we report that clean charge-two single-pair triple-point phonons appear in $P23$-type ${\mathrm{BeH}}_{2}$ and investigate the related chiral phonon transition under the uniaxial strains.