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Physical review, B. Condensed matter and materials physics
American Physical Society
Physical review, B. Condensed matter and materials physics

American Physical Society

周刊

1098-0121

Physical review, B. Condensed matter and materials physics/Journal Physical review, B. Condensed matter and materials physics
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    Average pure-state entanglement entropy in spin systems with SU(2) symmetry

    Rohit PatilLucas HacklGeorge R. FaganMarcos Rigol...
    245101.1-245101.15页
    查看更多>>摘要：We study the effect that the SU(2) symmetry, and the rich Hilbert space structure that it generates in lattice spin systems, has on the average entanglement entropy of highly excited eigenstates of local Hamiltonians and of random pure states. Focusing on the zero total magnetization sector (J_z = 0) for different fixed total spin J, we argue that the average entanglement entropy of highly excited eigenstates of quantum-chaotic Hamiltonians and of random pure states has a leading volume-law term whose coefficient s_A depends on the spin density j = J/(jL), with s_A(j →0) = ln(2j + 1) and s_A(j →1) =0, where j is the microscopic spin. We provide numerical evidence that s_A is smaller in highly excited eigenstates of integrable interacting Hamiltonians, which lends support to the expectation that the average eigenstate entanglement entropy can be used as a diagnostic of quantum chaos and integrability for Hamiltonians with non-Abelian symmetries. In the context of Hamiltonian eigenstates we consider spins j = 1/2 and 1, while for our calculations based on random pure states we focus on the spin j = 1/2 case.
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    • Amer Physical Soc

    Interplay between multispin and chiral spin interactions on a triangular lattice

    Li-Wei HeJian-Xin Li
    245102.1-245102.9页
    查看更多>>摘要：We investigate the spin-1/2 nearest-neighbor Heisenberg model with the four-site ring-exchange J_4 and chiral interaction J_χ on the triangular lattice by using the variational Monte Carlo method. The J_4 term induces the quadratic band touching (QBT) quantum spin liquid (QSL) with only a d + id spinon pairing (without hopping term), the nodal d-wave QSL and U (1) QSL with a finite spinon Fermi surface progressively. The effect of the chiral interaction J_χ can enrich the phase diagram with two interesting chiral QSLs (topological orders) with the same quantized Chern number C = 1/2 and ground-state degeneracy GSD = 2, namely the U(1) chiral spin liquid (CSL) and Z_2 d + id-wave QSL. The nodal d-wave QSL is fragile and will turn to the Z_2 d + id QSL with any finite J_χ within our numerical calculation. However, in the process from QBT to the Z_2 d + id QSL with the increase of J_χ, an exotic crossover region is found. In this region, the previous QBT state acquires a small hopping term so that it opens a small gap at the band touching points, and leads to an energy minimum which is energetically more favorable compared to another competitive local minimum from the Z_2 d + id QSL. We dub this state as the proximate QBT QSL and it gives way to the Z_2 d + id QSL eventually. Therefore, the cooperation of the J_4 and J_χ terms favors mostly the Z_2 d + id-wave QSL, so that this phase occupies the largest region in the phase diagram.
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    • Amer Physical Soc

    Higher-order topological phases hidden in quantum spin Hall insulators

    Baokai WangYi-Chun HungXiaoting ZhouArun Bansil...
    245103.1-245103.5页
    查看更多>>摘要：Topological materials burgeoned with the discovery of the quantum spin Hall insulators (QSHIs). Since their discovery, QSHIs have been viewed as being Z_2 topological insulators. This commonly held viewpoint, however, hides the far richer nature of the QSHI state. Unlike the Z_2 topological insulator, which hosts gapless boundary states protected by the time-reversal symmetry, the QSHI does not support gapless edge states because the spin-rotation symmetry breaks down in real systems. Here, we demonstrate that QSHIs hide higher-order topological insulator phases through two exemplar systems. We first consider the Kane-Mele model under an external field and show that it carries an odd spin Chern number C_s= 1. The model is found to host gapless edge states in the absence of Rashba spin-orbit coupling (SOC). But, a gap opens up in the edge spectrum when SOC is included, and the system turns into a higher-order topological insulator with in-gap corner states emerging in the spectrum of a nanodisk. We also discuss a time-reversal symmetric tight-binding model on a square lattice, and show that it carries an even spin Chern number C_s= 2. This unique phase has been taken to be topologically trivial because of its gapped edge spectrum. We show it supports in-gap comer states and hosts a higher-order topological phase.
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    • Amer Physical Soc

    Haldane phases and phase diagrams of the S = 3/2 and S = 1 bilinear-biquadratic Heisenberg model on the orthogonal dimer chain

    Ke RenMuwei WuShou-Shu GongDao-Xin Yao...
    245104.1-245104.14页
    查看更多>>摘要：We systematically study the effects of higher-order interactions on the S = 3/2, 1 orthogonal dimer chains using exact diagonalization and density matrix renormalization group. Due to frustration and higher spin, there are rich quantum phases, including three Haldane phases, two gapless phases, and several magnetically ordered phases. To characterize these phases and their phase transitions, we study various physical quantities such as energy gap, energy-level crossing, fidelity susceptibility, spin correlation, entanglement spectrum, and central charge. According to our calculations, the biquadratic term can enhance the Haldane phase regions. In particular, we numerically identify that a Haldane phase in S = 3/2 case is adiabatically connected to the exact AKLT (Affleck, Kennedy, Lieb, and Tasaki) point when adding a bicubic term. Our study on the orthogonal dimer model, which is a 1D version of the Shastry-Sutherland model, provides insights into understanding the possible S = 3/2, 1 Haldane phases in quasi-1D and 2D frustrated magnetic materials.
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    • Amer Physical Soc

    Orbital Hall effect in mesoscopic devices

    Diego B. FonsecaLucas L. A. PereiraAnderson L. R. Barbosa
    245105.1-245105.10页
    查看更多>>摘要：We investigate the orbital Hall effect through a mesoscopic device with momentum-space orbital texture that is connected to four semi-infinite terminals embedded in the Landauer-Buttiker configuration for quantum transport. We present analytical and numerical evidence that the orbital Hall current exhibits mesoscopic fluctuations, which can be interpreted in the framework of random matrix theory (RMT) (as with spin Hall current fluctuations). The mesoscopic fluctuations of orbital Hall current display two different amplitudes of 0.36 and 0.18 for weak and strong spin-orbit coupling, respectively. The amplitudes are obtained by analytical calculation via RMT and are supported by numerical calculations based on the tight-binding model. Furthermore, the orbital Hall current fluctuations lead to two relationships between the orbital Hall angle and conductivity. Finally, we confront the two relations with experimental data of the orbital Hall angle, which shows good concordance between theory and experiment.
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    • NETL
    • NSTL
    • Amer Physical Soc

    Emergent SU(8) Dirac semimetal and proximate phases of spin-orbit coupled fermions on a honeycomb lattice

    Basudeb MondalVijay B. ShenoySubhro Bhattacharjee
    245106.1-245106.47页
    查看更多>>摘要：Emergent Dirac fermions provide the starting point for understanding the plethora of novel condensed matter phases. The nature of the associated phases and phase transitions crucially depends on both the emergent symmetries as well as the implementation of the microscopic ones on the low-energy Dirac fermions. Here, we show that j = 3/2 electrons in spin-orbit coupled materials on honeycomb lattice can give rise to SU(8) symmetric Dirac semimetals with symmetry implementation very different from that of graphene. This nontrivial embedding of the microscopic symmetries in the low energy is reflected in the nature of phases proximate to the Dirac semimetal. Such phases can arise from finite short-range electron-electron interactions. In particular, we identify 24 such phases-divided into three classes-and their low-energy properties obtained by condensing particle-number conserving fermion bilinears that break very different microscopic symmetries and/or are topologically protected by symmetries. The latter includes interesting generalizations of quantum spin-Hall phases. Remarkably some of the resultant phases still support a subset of gapless fermions-protected by a subgroup of SU(8)-resulting in interesting density wave semimetals. Near the phase transitions to such density wave semimetals, the surviving gapless fermions strongly interact with the bosonic order parameter field and give rise to novel quantum critical points. Our study is applicable to a wide class of d~1 and d~3 transition metals with strong spin-orbit coupling and predicts that such materials can harbor a very rich interplay of symmetries and competing interactions in the intermediate correlation regime.
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    • NSTL
    • Amer Physical Soc

    Excitonic properties of clustered-Pl borophene

    Vaishnavi VishnubhotlaSantanu MahapatraSitangshu Bhattacharya
    245107.1-245107.13页
    查看更多>>摘要：Using rigorous ab initio calculations of many-body electron-electron, electron-phonon, electron-hole, and exciton-phonon couplings, we demonstrate that the recently discovered semiconducting phase, clustered-P1 borophene, can exhibit an optical gap of 0.74 eV and possesses a substantial binding energy of 1.5 eV at room temperature. Additionally, it features a significantly faster nonradiative recombination rate at room temperature. The profound impact of dynamical self-energies originating from pure electron-phonon interactions results in a noteworthy zero-point renormalization of the quasiparticle direct and indirect gaps, leading to large shifts of 73 and 91 meV, respectively. We demonstrate strong, incoherent interactions between electrons and holes with lattice vibrations, resulting in a significant redshifting of the absorption spectrum at 0 K. The pivotal phonon modes responsible for shaping the lowest bound exciton originates from the spectral range of 350-950 cm~(-1) and also exhibits resilience against temperature variations. Notably, the room temperature nonradiative lifetime of the lowest bound exciton is found to be significantly smaller (～40 fs) compared to its intrinsic radiative lifetime (～0.6 ns). These remarkable outcomes collectively suggest that clustered-P1 borophene is a formidable contender for the development of near-ultraviolet optoelectronic devices.
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    • NSTL
    • Amer Physical Soc

    Influence of a realistic multiorbital band structure on conducting domain walls in perovskite ferroelectrics

    B. C. CornellW. A. Atkinson
    245108.1-245108.12页
    查看更多>>摘要：Domain wall morphologies in ferroelectrics are believed to be largely shaped by electrostatic forces. Here, we show that for conducting domain walls, the morphology also depends on the details of the charge-carrier band structure. For concreteness, we focus on transition-metal perovskites like BaTiO_3 and SrTiO_3. These have a triplet of t_(2g) orbitals attached to the Ti atoms that form the conduction bands when electron doped. We solve a set of coupled equations-Landau-Ginzburg-Devonshire (LGD) equations for the polarization, tight-binding Schrodinger equations for the electron bands, and Gauss' law for the electric potential-to obtain polarization and electron density profiles as a function of electron density. We find that at low electron densities, the electron gas is pinned to the surfaces of the ferroelectric by a Kittel-like domain structure. As the electron density increases, the domain wall evolves smoothly through a zigzag head-to-head structure, eventually becoming a flat head-to-head domain wall at high density. We find that the Kittel-like morphology is protected by orbital asymmetry at low electron densities, while at large electron densities the high density of states of the multiorbital band structure provides effective screening of depolarizing fields and flattens the domain wall relative to single-orbital models. Finally, we show that in the zigzag phase, the electron gas develops tails that extend away from the domain wall, in contrast to naive expectations.
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    • Amer Physical Soc

    Revisiting Bloch electrons in a magnetic field: Hofstadter physics via hybrid Wannier states

    Xiaoyu WangOskar Vafek
    245109.1-245109.14页
    查看更多>>摘要：We revisit the Hofstadter butterfly for a subset of topologically trivial Bloch bands arising from a continuum free electron Hamiltonian in a periodic lattice potential. We employ the recently developed procedure, which was previously used to analyze the case of topologically nontrivial bands [Wang and Vafek, Phys. Rev. B 106, L121111 (2022)], to construct the finite-field Hilbert space from the zero-field hybrid Wannier basis states. Such states are Bloch extended along one direction and exponentially localized along the other. The method is illustrated for square and triangular lattice potentials and is shown to reproduce all the main features of the Hofstadter spectrum obtained from a numerically exact Landau level expansion method. In the regime where magnetic length is much longer than the spatial extent of the hybrid Wannier state in the localized direction we recover the well-known Harper equation. Because the method applies to both topologically trivial and nontrivial bands, it provides an alternative and efficient approach to moire materials in magnetic field.
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    • Amer Physical Soc

    Dirac Kondo effect under magnetic catalysis

    Koichi HattoriDaiki SuenagaKei SuzukiShigehiro Yasui...
    245110.1-245110.11页
    查看更多>>摘要：We develop a mean-field theory of a novel Kondo effect emerging in systems without a Fermi surface, which instead emerges under strong magnetic fields. We determine the magnitude of the Kondo condensate, which is a particle pairing composed of conducting Dirac fermions and localized impurities. We focus on the competition between the Kondo effect and the energy gap formation that stems from the pairing among the Dirac fermions leading to the dynamical chiral symmetry breaking. We find that this competition induces a quantum critical point. We also investigate finite-temperature effects. This system at vanishing fermion density can be studied with Monte Carlo lattice simulations, which do not suffer from the sign problem.
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    • NSTL
    • Amer Physical Soc