Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session F54: Advances in the Integer Quantum Hall Effect 
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Sponsoring Units: DCMP Chair: Oscar Bernal, Cal State Univ LA Room: Mile High Ballroom 2A 
Tuesday, March 3, 2020 8:00AM  8:12AM 
F54.00001: ChalkerCoddington network model as a Floquet topological insulator Victor Gurarie, Andrew Potter We reexamine the ChalkerCoddington network model, which was originally introduced to model integer quantum Hall plateau transitions. We point out that the dynamics of this model actually describe a periodicallydriven (Floquet) system whose bands have vanishing Chern number throughout the phase diagram. Instead, the topological phase of the network model arises from a nontrivial dynamical Floquet invariant, i.e. the network model describes transitions between trivial and chiral Floquet phases of a distinct topological class from the integer quantum Hall effect. In view of this observation, we reevaluate the standard arguments given in the past that the quantum Hall plateau transition and the transition in the ChalkerCoddington network model belong to the same universality class. 
Tuesday, March 3, 2020 8:12AM  8:24AM 
F54.00002: Quantum Hall Effect in QuasiOneDimensional Weak Topological Insulator Tianyi Xu, Patrick Cheung, Fengcheng Wu, Fan Zhang Prototypical weak topological insulators (WTI) have been theoretically predicted to be realized in quasionedimensional materials Bi_{4}X_{4 }(X = Br, I)_{ }[PRL 116, 066801 (2016)] and then experimentally confirmed in ARPES [Nature (London) 566, 518 (2019)]. The unique surface states of such a WTI have two entangled Dirac cones with strong anisotropy. We study theoretically the integer quantum Hall effect of such WTI surface states and show the important roles played by the special geometry, symmetry, topology, and their interplay in Bi_{4}X_{4}. We also predict prominent signatures in transport experiments. 
Tuesday, March 3, 2020 8:24AM  8:36AM 
F54.00003: Noninteracting and interacting Graphene in a strong uniform magnetic field Ankur Das, Ribhu Kaul, Ganpathy Murthy We study monolayer graphene in a uniform magnetic field in the absence and presence of interactions. In the noninteracting limit for p/q flux quanta per unit cell, the central two bands have 2q Dirac points in the Brillouin zone in the nearestneighbor model. These touchings and their locations are guaranteed by chiral symmetry and the lattice symmetries of the honeycomb structure. If we add a staggered potential and a next nearest neighbor hopping we find their competition leads to a topological phase transition. We also study the stability of the Dirac touchings to onebody perturbations that explicitly lowers the symmetry. 
Tuesday, March 3, 2020 8:36AM  8:48AM 
F54.00004: Quantum Hall Effect in Chiralityinduced Weyl Semiconductor ntype Tellurene Gang Qiu, Chang Niu, Yixiu Wang, Mengwei Si, Wenzhuo Wu, Peide (Peter) Ye Very recently a new mechanism of generating Weyl nodes were proposed in chiral crystals with strong spinorbit coupling, which, in sharp contrast to conventional bandinversioninduced Weyl semimetals, can exist in semiconductor systems. Tellurium (Te) is predicted to have these Weyl nodes located at the edge of the conduction band, originated from its DNAlike chiral chain crystal structure. However Te is naturally ptype doped and its conduction band has rarely been studied through transport measurement. In this work we report the first quantum Hall experiment in ALD doped ntype 2D tellurium (dubbed as tellurene) samples with mobility 6,000 cm^{2}/Vs. The chiralityinduced Weyl nodes give rise to radial spin texture, and topologically nontrivial π Berry phase was detected in quantum Hall sequences. Additionally, the doping profile forms a wide quantum well with symmetricantisymmetric energy states leading to an approximate SU(8) isospin symmetry. Our work expands the spectrum of Weyl matters into semiconductor regime for the first time. 
Tuesday, March 3, 2020 8:48AM  9:00AM 
F54.00005: Chiral quasiparticle tunneling between quantum Hall edges in proximity with a superconductor Ivan Borzenets, MingTso Wei, Anne M Draelos, Andrew Seredinski, ChungTing Ke, Kenji Watanabe, Takashi Taniguchi, Michihisa Yamamoto, Seigo Tarucha, Francois Amet, Gleb Finkelstein We study a twoterminal graphene Josephson junction with contacts shaped to form a narrow constriction, 
Tuesday, March 3, 2020 9:00AM  9:12AM 
F54.00006: Hall and dissipative viscosity and conductivity in a disordered 2D electron gas Igor Burmistrov, Moshe Goldstein, Mordecai Kot, Vladislav Kurilovich, Pavel Kurilovich Hydrodynamic charge transport is at the center of recent research efforts. Of particular interest is the nondissipative Hall viscosity, which conveys topological information in clean gapped systems. The prevalence of disorder in the real world calls for a study of its effect on viscosity, as well as on its relation with the nonlocal conductivity, the main venue to its experimental measurement. Here we address this question for disordered noninteracting 2D electrons. Analytically, we employ the selfconsistent Born approximation, accounting for the modification of the singleparticle density of states and the elastic transport time by the Landau quantization. Our results interpolate smoothly between the limiting cases of weak (strong) magnetic field and strong (weak) disorder. In the regime of weak magnetic field we describe the quantum (Shubnikovde Haas type) oscillations of the viscosity, nonlocal conductivity, and WenZee response. For strong magnetic fields we characterize the effects of the disorderinduced broadening of the Landau levels on the transport coefficients. This is supplemented by numerical calculations for a few filled Landau levels. Our results show that the Hall viscosity and its relation with conductivity are surprisingly robust to disorder. 
Tuesday, March 3, 2020 9:12AM  9:24AM 
F54.00007: Geometric entanglement in integer quantum Hall states Lucie Fournier, William WitczakKrempa We study the structure of entanglement in integer quantum Hall states using the entanglement entropy (EE) as well as the reduced density matrix, through its spectrum and eigenstates. We focus on an important class of spatial regions that have a sharp corner, which leads to an angledependent contribution to the EE. We unravel surprising relations by comparing this corner term at different fillings. We further find that the corner term, when properly normalized, has nearly the same angle dependence as conformal theories in 2 spatial dimensions. We also reveal that the lowlying entanglement spectrum and corresponding eigenfunctions describe edge excitations localized at the corner. Finally, we present an outlook for fractional quantum Hall states. 
Tuesday, March 3, 2020 9:24AM  9:36AM 
F54.00008: Strongdisorder renormalization group approach to the integer quantum Hall effect João Getelina, Martin Puschmann, Jose A Hoyos, Thomas Vojta The critical behavior of the integer quantum Hall transition has recently reattracted considerable attention [1]. We propose an alternative numerical approach, namely a modified strongdisorder renormalization group (SDRG) method, in order to investigate this transition. The SDRG method is a recursive decimation process which is known to yield exact results for electronic tightbinding models, provided one keeps all links generated under renormalization. In practical applications, the number of kept links is limited. Nonetheless, in a recent study of the Anderson localization transition, it has been shown that one can get reasonable results for the critical exponents by keeping only a relatively small maximum number of links per site [2]. We generalize this method to the integer quantum Hall problem and apply it to both square lattice and long strip geometries. 
Tuesday, March 3, 2020 9:36AM  9:48AM 
F54.00009: Nonlocal induced pairing in chiral edge states Andreas Michelsen, Patrik Recher, Bernd H. Braunecker, Thomas Schmidt A superconductor in contact with a quantum Hall material will induce fundamentally nonlocal superconducting correlations in the quantum Hall edge state through the proximity effect. Such correlations are often put into models by hand in local approximations, but by building a model without assumed locality we are able predict the strength and nonlocal spatiotemporal behaviour of the correlation. Accurately modelling this correlation allows us to treat geometries of experimental interest and predict the behavior of interesting effects such as crossed Andreev reflection. This is relevant for several recent experiments, and the treated hybridized state has been proposed as part of a system hosting nonAbelian anyonic zero modes. 
Tuesday, March 3, 2020 9:48AM  10:00AM 
F54.00010: Reconstruction near the interface of a ν=4 and ν=3 QH systems Amartya Saha, Suman De, Ganpathy Murthy, Sumathi Rao, Yuval Gefen We study the HartreeFock ground state near the interface between the ν=4 and ν=3 quantum Hall systems. In this problem we have two tuning parameters, w which is the width of interface in units of l (magnetic length), and Ec which is the strength of coulomb interaction in units of the cyclotron energy. In the bulk, for 2.52 < Ec <2.94, the ν=3 state is fully polarised but ν=4 state is a singlet. We have found that in this regime there are two edge phases. Phase 1 has 3 chiral modes, 2 downstream and 1 upstream. In this phase spin is a good quantum number. In Phase 2 we only found 1 chiral mode which is downstream. This phase has a spin rotation and can have a pair of counter propagating neutral modes. We use the time dependent HartreeFock method to calculate the collective excitations of these phases. 
Tuesday, March 3, 2020 10:00AM  10:12AM 
F54.00011: Spin1 Photonic Skyrmion in Viscous Quantum Hall Fluids Todd Van Mechelen, Zubin Jacob We present the fundamental model of a topological electromagnetic phase of matter: viscous MaxwellChernSimons theory. We demonstrate that this is the minimal (exactly solvable) gauge theory with a nontrivial photonic Chern number. The interplay of symmetry and topology is also captured in the Chern number, which is determined by the spin1 representations of a photonic skyrmion at highsymmetry points in the Brillouin zone. Physically, our predicted electromagnetic phases are connected to a dynamical photonic mass in a viscous quantum Hall fluid. The electromagnetic phase is topologically nontrivial when the Hall viscosity inhibits the total bulk Hall response. Our work bridges the gap between electromagnetic and condensed matter topological physics while also demonstrating the central role of spin1 quantization in nontrivial photonic phases. 
Tuesday, March 3, 2020 10:12AM  10:24AM 
F54.00012: Excited quantum Hall effect: enantiomorphic flat bands in a YinYang Kagome lattice Yinong Zhou, Gurjyot Sethi, Hang Liu, Zhengfei Wang, Feng Liu Quantum Hall effect (QHE) is one of the most fruitful research topics in condensedmatter physics. Ordinarily, the QHE manifests in a ground state with timereversal symmetry broken by magnetization to carry a quantized chiral edge conductivity around a twodimensional insulating bulk. We propose a theoretical concept and model of nonequilibrium excitedstate QHE (EQHE) without intrinsic magnetization. It arises from circularly polarized photoexcitation between two enantiomorphic flat bands of opposite chirality, each supporting originally a helical topological insulating state hosted in a YinYang Kagome lattice. The chirality of its edge state can be reversed by the handedness of light, instead of the direction of magnetization as in the conventional quantum (anomalous) Hall effect, offering a simple switching mechanism for quantum devices. Implications and realization of EQHE in real materials are discussed. 
Tuesday, March 3, 2020 10:24AM  10:36AM 
F54.00013: ferromagnetic transition in chiral metal Tongtong Liu, Zhen Bi, Sungjoon Hong, Liang Fu This letter studies a spinful 1D chiral electron model with contact interaction and nonlinear dispersion, where an itinerant ferromagnetic phase transition happens at repulsive interaction and an Amperean pairing at attractive interaction, the two phases are symmetrical and connected by a particlehole transformation. We use bosonization and relate it with the fermion model to study the phase transition criticality and find the spin and charge modes have different dynamical exponent, which leads to a fractionalpower time correlation, unlike the Luttinger liquid theory. We also find a similar transition in the quantum Hall edge states, the nonlinear dispersion is replaced with the presence of interaction form factor after projecting to the Landau levels. 
Tuesday, March 3, 2020 10:36AM  10:48AM 
F54.00014: van der Waals Heterostructures of 3D Topological Insulators and 2D Magnetic Materials Shuwan Liu, Su Kong Chong, Taylor D. Sparks, Vikram V Deshpande Three dimensional (3D) topological insulator (TI) based van der Waals heterostructures form an excellent platform to study the proximity effect between a TI surface and another layered material, such as a twodimensional (2D) ferromagnet. Previously we have observed both massless relativistic Dirac fermions and massive (gapped) Dirac fermions in this way for the topological surface state of BiSbTeSe_{2}^{1} and have reported quantum Hall data for these surfaces. However, typical ferromagnets get oxidized easily during the fabrication process. Thus, the induced magnetization in the TI interface is not clean under ambient conditions. To minimize the influence of oxidation, we explore this fabrication inside a glovebox. We will report the performance of such TI based devices in comparison to those builtin ambient conditions and further study the proximity effect in TIbased van der Waals heterostructures. 

F54.00015: Phase transition and anomalous scaling in the quantum Hall transport of topologicalinsulator SnBi_{1.1}Sb_{0.9}Te_{2}S devices Faji Xie, Shuai Zhang, Fengqi Song The scaling physics of quantum Hall transport in optimized topological insulators with a plateau precision of ∼1/1000 e^{2}/h is considered. Two exponential scaling regimes are observed in temperaturedependent transport dissipation, one of which accords with thermalactivation behavior with a gap of 2.8 meV (>20 K), the other being attributed to variablerange hopping (1–20 K). Magneticfielddriven plateautoplateau transition gives scaling relations of (dR_{xy}/dB)^{max} ∝ T ^{−κ} and △B^{−1} ∝ T ^{−κ }with a onsistent exponent of κ ∼ 0.2, which is half the universal value for a conventional twodimensional electron gas. This is evidence of percolation assisted by quantum tunneling and reveals the dominance of electronelectron interaction of the topological surface states. 
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