Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S56: Topology and Correlations 
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Sponsoring Units: DCMP Chair: Narayan Poudel, Idaho National Laboratory Room: Mile High Ballroom 2C 
Thursday, March 5, 2020 11:15AM  11:27AM 
S56.00001: Optical Evidence of an Enhanced Electronic Effective Mass in the Anomalous Pb_{1x}Tl_{x}Te Superconductor Leonardo Degiorgi, Manuel Chinotti, Anirban Pal The narrow bandgap semiconductor PbTe exhibits a number of striking properties upon thallium (Tl)doping, including the onset of superconductivity at temperatures T_{c }which are substantially higher than for materials with equivalent charge carrier concentration. Here, we provide a thorough optical investigation of Pb_{1x}Tl_{x}Te over a very broad spectral range and contrast its normalstate, complete excitation spectrum with the optical response of the nonsuperconducting analog Nadoped PbTe [1]. We capture the relevant energy scales shaping their electronic structure and uncover the formation of an impurity band upon doping with Tl, which evolves into a resonant state for large doping. This implies a large density of states and an enhancement of the optical effective mass m*/m_{e }of the itinerant charge carriers, which is stronger for Tl than for Nadoping. Since the enhancement of m*/m_{e }particularly occurs upon crossing a critical concentration x_{c }in Tldoped PbTe for which T_{c}≠ 0, we advance its relevance for the onset of superconductivity. 
Thursday, March 5, 2020 11:27AM  11:39AM 
S56.00002: WeylKondo semimetal: controlling the nodes via magnetic field Sarah Grefe, HsinHua Lai, Silke BuehlerPaschen, Qimiao Si In the effort to study topological metals in stronglycorrelated settings, a WeylKondo semimetal (WKSM) has been concurrently discovered in theoretical^{1} and experimental^{2,3} studies. This timereversalinvariant state appears in a noncentrosymmetric Kondo lattice model. The theoretical and experimental signatures of the WKSM phase, include correlationsenhanced specific heat C=Γ T^{3} and a giant topological Hall response from the Kondodriven Weyl nodes being pinned near the Fermi energy. Recently, high magnetic field experiments revealed a twostage quantum phase transition, including a topological transition from the WKSM to a Kondo insulator.^{4} To connect with these experiments, we studied an Anderson lattice model with terms that break both time reversal and inversion symmetries.^{5} Tuning these terms controls the position and number of Weyl nodes in the Brillouin zone, and several topologically distinct phases emerge in this model. 
Thursday, March 5, 2020 11:39AM  11:51AM 
S56.00003: Quasiparticles as Detector of Topological Quantum Phase Transitions Sourav Manna, Nagara Srinivasa Prasanna Srivatsa, Julia Wildeboer, Anne E. B. Nielsen Phases and phase transitions provide an important framework to understand the physics of strongly correlated quantum manybody systems. Topologically ordered phases of matter are particularly challenging in this context, because they are characterized by longrange entanglement and go beyond the LandauGinzburg theory. A few tools have been developed to study topological phase transitions, but the needed computations are generally demanding, they typically require the system to have particular boundary conditions, and they often provide only partial information. There is hence a high demand for developing further probes. Here, we propose to use the study of quasiparticle properties to detect phase transitions. Topologically ordered states support anyonic quasiparticles with special braiding properties and fractional charge. Being able to generate a given type of anyons in a system is a direct method to detect the topology, and the approach is independent from the choice of boundary conditions. We provide three examples, and for all of them we find that it is sufficient to study the anyon charge to detect the phase transition point. This makes the method numerically cheap. 
Thursday, March 5, 2020 11:51AM  12:03PM 
S56.00004: Higherform symmetry perspective on fracton phases Marvin Qi, Leo Radzihovsky, Michael A Hermele Higher form symmetry provides a framework to understand some aspects of topologically ordered phases. Motivated by this, we study the role that higher form symmetry plays in the context of fracton phases. We introduce the notion of a nonfaithful higher form symmetry and describe how fractons can arise via condensation of objects charged under such a symmetry. Finally we describe how such a nonfaithful higher form symmetry can arise as a quotient of an ordinary higherform symmetry via gauging certain subgroups. 
Thursday, March 5, 2020 12:03PM  12:15PM 
S56.00005: Local and Nonlocal correlation effects in topological quantum phase transitions Lorenzo Crippa, Adriano Amaricci, Giorgio Sangiovanni, Massimo Capone The fate of quantum phase transition among different topological states in presence of strong interaction is of primary interest in condensed matter. 
Thursday, March 5, 2020 12:15PM  12:27PM 
S56.00006: Anomalous localization at the boundary of an interacting topological insulator Itamar Kimchi, YangZhi Chou, Rahul Nandkishore, Leo Radzihovsky The boundary of a topological insulator (TI) hosts an anomaly restricting its possible phases: e.g. 3D strong and weak TIs maintain surface conductivity at any disorder if symmetry is preserved onaverage, at least when electron interactions on the surface are weak. However the interplay of strong interactions and disorder with the boundary anomaly has not been well studied theoretically. Here we present our results on this combination, for the edge of a 2D TI and the surface of a 3D weak TI, showing how it can lead to an "Anomalous Many Body Localized" (AMBL) phase that preserves the anomaly. We discuss its anomaly manifestation, predictions for experimental observations, and theoretical consequences for understanding 3D TIs and anomaly restrictions. 
Thursday, March 5, 2020 12:27PM  12:39PM 
S56.00007: Interaction effects on centrosymmetric Bogoliubov Fermi surfaces Hanbit Oh, EunGook Moon Exotic quantum phases including topological insulators/semimetals and nonFermi liquids may be realized by quantum states with total angular momentum j=3/2 as manifested in HgTe and pyrochlore iridates. Recently, an exotic superconducting state with a finite density of zero energy Bogoliubov quasiparticles, Bogoliubov Fermisurface, was also proposed in a centrosymmetric j=3/2 system with a Z2 topological invariant. We consider interaction effects of the Bogoliubov Fermi surfaces by using standard renormalization group and meanfield theory and discuss the implication of inversion symmetry breaking. Possible applications of our theory to iron based superconductors and heavy fermion systems including FeSe are also discussed 
Thursday, March 5, 2020 12:39PM  12:51PM 
S56.00008: Twisted dualities and the 2d Majorana checkerboard Marcus Bintz Large ensembles of bound Majorana modes can form their own stronglyinteracting phases of matter. For example, a square lattice of Majoranas coupled purely by fourfermion plaquette terms may be the effective description for the vortex lattice on the surface of certain 3d topological insulators. This talk leverages recently formulated exact dualities to derive novel representations of such a 2d Majorana checkerboard. Some connections to quantum cellular automata (QCA) and subsystem symmetry protected topological order (SSPT) are also discussed. 
Thursday, March 5, 2020 12:51PM  1:03PM 
S56.00009: Universal SPT invariants using swap operators Shriya Pai, Michael A Hermele We will describe manybody topological invariants/order parameters for SPT phases that involve acting with symmetry operators and a swap operator. To do so, we use the universal notion of distinguishing between different phases of matter: phases are equivalence classes defined in the thermodynamic limit by (i) adiabatic continuity, and (ii) adding trivial degrees of freedom. In the process, we will also formulate gaugeinvariant versions of these order parameters. Since our arguments for the universality of such manybody invariants do not depend on the spatial dimension we are working in, this discussion can help serve as a basis for generalizations to higher spatial dimensions. We will also show how to picture the invariant by putting the system on a spacetime manifold and by thinking in terms of TQFT partition functions. 
Thursday, March 5, 2020 1:03PM  1:15PM 
S56.00010: Exceptionaltorus in strongly correlated nodalline semimetals with manybody chiral symmetry Kazuhiro Kimura, Tsuneya Yoshida, Norio Kawakami Recent studies have revealed a new type of topological phase described by a nonHermitian (NH) Hamiltonian. In equilibrium systems, if we describe the energy spectrum of quasiparticles having the complex selfenergy in terms of effective Hamiltonian, NH physics naturally shows up because of the life time effects from selfenergy. The most important point is the emergence of gapless defective points (DPs), which lead to an open Fermi surface, such as Fermi arcs in the bulk energy spectrum. 
Thursday, March 5, 2020 1:15PM  1:27PM 
S56.00011: Realizing the Majorana Quasiparticle fermionic dynamics in \emph{(1+1)} dimensional Topological Quantum Materials Sushant Kumar Behera, Pritam Deb A Majorana fermion and its dynamics are determined by the Majorana equation having equal values of spinor and conjugate field, thereby making topological quantum material a technological reality [\emph{Phys. Rev. Lett.} $\bf{121}$, 067701, 2018]. It is interesting to study the dynamics of Majorana fermions in presence of external perturbations in \emph{(1+1)} dimensions, a scalar potential by approaching for the first time implementing the methods of supersymmetric quantum mechanics [\emph{Phys. Rev. Lett.} $\bf{106}$, 060503, 2011; \emph{Rev. Mod. Phys.} $\bf{80}$, 1083, 2008]. Moreover, the dynamics of two competing effects (i.e. strain and magnetic field) is worth to focus in monolayer quantum material with the aim to explore its impact in various phenomena of quantum field theory, such as induced charge density, magnetic catalysis, symmetry breaking, dynamical mass generation, and magnetization. The combined effect of real and pseudomagnetic fields produces an induced valley polarization creating new platforms to design quantum computers and valleytronics devices. 
Thursday, March 5, 2020 1:27PM  1:39PM 
S56.00012: CrystaltoFracton Tensor Gauge Theory Dualities Zhengzheng Zhai, Michael Pretko, Leo Radzihovsky We discuss the duality between elasticity of twodimensional crystals and fracton tensor gauge 
Thursday, March 5, 2020 1:39PM  1:51PM 
S56.00013: Interactions in nodalline semimetals with quadratic band touching Geo Jose, Bruno Uchoa We address the problem of Coloumb interactions in 3D nodalline semimetals with quadratic band touching using perturbative Wilsonian renormalization group approach. At one loop order, we find that the noninteracting fixed point is unstable and flows to an interacting fixed point. We compute corrections to the dynamical exponent, the screening charge and find corrections to other experimentally measurable quantities such as the specific heat, compressibility, etc. We also consider the emergence of other competing instabilities in the charge sector from shortrange interactions. 
Thursday, March 5, 2020 1:51PM  2:03PM 
S56.00014: Statistical localization: from strong fragmentation to strong edge modes Tibor Rakovszky, Pablo Sala de TorresSolanot, Ruben Verresen, Michael Knap, Frank Pollmann Certain disorderfree Hamiltonians can be nonergodic due to a strong fragmentation of the Hilbert space into disconnected sectors. We show how to characterize such systems by introducing the notion of 'statistically localized integrals of motion’ (SLIOM), whose eigenvalues label the connected components of the Hilbert space. SLIOMs are not spatially localized in the operator sense, but appear localized to subextensive regions when their expectation value is taken in typical states with a finite density of particles. We will illustrate this general concept on several Hamiltonians, both with and without dipole conservation. For the former we uncover additional SLIOMs due to dipole moment conservation on finite regions of the chain. Moreover, we explain that there exist perturbations which destroy these integrals of motion in the bulk of the system, while keeping them on the boundary. This results in statistically localized strong zero modes, leading to infinitely longlived edge magnetizations along with a thermalizing bulk. We also show that these edge modes can lead to the appearance of topological string order in a certain subset of highly excited eigenstates, and conclude providing experimental realizations of these models using existing experimental platforms. 

S56.00015: Classification of topological phases in one dimensional nonhermitian systems Wenjie Xi, Zhihao Zhang, Zhengcheng Gu, Weiqiang Chen Topological phases in nonHermitian systems became a fascnating subject recently. In this paper, we attempt to classify topological phases in 1D nonHermitian systems. We begin with the nonHermitian generalization of SuSchriefferHeeger(SSH) model and discuss its many body topological Berry phase, which is well defined for any quasi hermitian systems(nonHermitian systems that have real energy spectrum). 
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