Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S43: Correlated Topological States in Lower DimensionLive
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Yize Li, California State University, Bakersfield |
Thursday, March 18, 2021 11:30AM - 11:42AM Live |
S43.00001: Competing phases and their selection in two-dimensional doped Dirac and Luttinger liquid Andras Szabo, Bitan Roy We consider the problem of interacting spinful electrons in mono- and bilayer graphene both at zero and at finite temperature and chemical doping. Due to the many degrees of freedom, there are a plethora of available broken symmetry phases competing for nucleation. We shed light on the structure of the global phase diagrams using a set of selection rules, applicable in various strongly correlated multiband systems. We exemplify these selection rules by considering the phase diagram of the honeycomb Hubbard model. |
Thursday, March 18, 2021 11:42AM - 11:54AM Live |
S43.00002: Fractonic topological phases from coupled wires Joseph Sullivan, Arpit Dua, Meng Cheng We explore fractonic topological phases using three-dimensional coupled wire constructions, which have proven to be a successful tool to realize and characterize topological phases in two dimensions. We find that both gapped and gapless phases with fractonic excitations can emerge from the models. We show that the excitations in general have infinite-order fusion structure, distinct from previously known gapped fracton models. Like the 2D coupled wire constructions, many models exhibit gapless (or even chiral) surface states, which can be described by infinite-component Luttinger liquids. However, the universality class of the surface theory strongly depends on the surface orientation, thus revealing a new type of bulk-boundary correspondence unique to fracton phases. |
Thursday, March 18, 2021 11:54AM - 12:06PM Live |
S43.00003: DMRG evidence for superconductivity via skyrmion-condensation: Application to magic angle graphene Shubhayu Chatterjee, Matteo Ippoliti, Michael Zaletel We numerically study the fate of interacting electrons in tunnel-coupled spinful Chern bands with opposite Chern numbers using density-matrix renormalization group (DMRG). Such a model has been argued to capture the essential symmetries and band topology of magic angle twisted bilayer graphene. On doping away from the antiferromagnetic insulator at charge neutrality, we find a superconducting ground state, although the inter-electronic interaction is purely repulsive. By studying the energetics of charged excitations, we establish that superconductivity is driven by the binding of electrons into charge-2e bosonic skyrmions which subsequently condense. This binding is observed even in the regime where the Coulomb repulsion is by-far the largest energy scale, demonstrating the robustness of this topological, all-electronic pairing mechanism. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S43.00004: Topological edge and interface states at bulk disorder-to-order quantum critical points Yichen Xu, Xiaochuan Wu, Chao-Ming Jian, Cenke Xu We study the interplay between two nontrivial boundary effects: (1) the two-dimensional (2d) edge states of three-dimensional (3d) strongly interacting bosonic symmetry-protected topological states, and (2) the boundary fluctuations of 3d bulk disorder-to-order phase transitions. We then generalize our study to 2d gapless states localized at an interface embedded in a 3d bulk, when the bulk undergoes a quantum phase transition. Our study is based on generic long-wavelength descriptions of these systems and controlled analytic calculations. Our results are summarized as follows: (i) The edge state of a prototype bosonic symmetry-protected state can be driven to a new fixed point by coupling to the boundary fluctuations of a bulk quantum phase transition; (ii) the states localized at a 2d interface of a 3d SU(N) quantum antiferromagnet may be driven to a new fixed point by coupling to the bulk quantum critical modes. Properties of the new fixed points identified are also studied. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S43.00005: Lieb-Schultz-Mattis type theorems for Majorana chains with discrete symmetries Ömer Mert Aksoy, Apoorv Tiwari, Christopher M Mudry A central question in condensed matter physics is to compute the degeneracy of the ground state and decide if the excitations are gapped or gapless, given a microscopic Hamiltonian with certain local degrees of freedom. The Lieb-Schultz-Mattis theorems are (no-go) theorems that constrain the possible answers to this question. We derive a set of Lieb-Schultz-Mattis type constraints in (1+1)-dimensional spacetime relevant to the local Hamiltonians represented by Majorana fermions that are invariant under discrete symmetries. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S43.00006: Level statistics of the strained Kitaev honeycomb model with Heisenberg interactions and disorder Mikael Fremling, Lars Fritz We study the Kitaev honeycomb spin model in the presence of geometric strain and weak residual Heisenberg interactions. Similarly to graphene, as triaxial strain is applied, flat bands appear resembling Landau levels for the Majorana fermions. It is known that weak Heisenberg interactions that don't take you out of the ground state flux sector lead to an effective interaction term between the Majoranas. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S43.00007: Subdiffusive dynamics and critical quantum correlations in a disorder-free localized Kitaev honeycomb model Guo-Yi Zhu, Markus Heyl Disorder-free localization has recently emerged as a mechanism for ergodicity breaking in homogeneous lattice gauge theories. In this work we show that this mechanism can lead to unconventional states of quantum matter as the absence of thermalization lifts constraints imposed by equilibrium statistical physics. We study a Kitaev honeycomb model in a skew magnetic field subject to a quantum quench from a fully polarized initial product state and observe nonergodic dynamics as a consequence of disorder-free localization. We find that the system exhibits a subballistic entanglement growth and quantum correlation spreading, which is otherwise typically associated with thermalizing systems. In the asymptotic steady state the Kitaev model develops volume-law entanglement and power-law decaying dimer quantum correlations at an energy density where the equilibrium model only displays paramagnetic and noncritical properties. Our work sheds light onto the potential for disorder-free localized lattice gauge theories to realize quantum states in two dimensions with properties beyond what is possible in an equilibrium context. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S43.00008: Non-abelian anyons induced by spontaneous symmetry breaking in a generalized Kitaev spin liquid model Bo-Hai Li, Hao-Xin Wang, Hong Yao Non-abelian anyons have been proved to be generated in Kitaev's quantum spin liquid by magnetic field. That enables the error-correcting topological quantum computation (TQC) to be performed. Spontaneous symmetry breaking induced non-abelian phase, rather than field-induced one, is better candidate for TQC in real materials. We propose an extended-Kitaev model on spin-1/2 honeycomb models with time-reversal-preserving interaction. Numerical evidence of spontaneous time-reversal-symmetry breaking is observed and supposed to possess non-abelian anyons. That makes it the first quantum spin liquid to generate non-abelian statistics through spontaneous symmetry breaking. |
Thursday, March 18, 2021 1:06PM - 1:18PM Live |
S43.00009: Emergent symmetries in the global phase diagram of two-dimensional extended honeycomb-Hubbard model Bitan Roy Massless Dirac fermions realized as low-energy emergent quasiparticles in carbon-based monolayer honeycomb membrane constitute an ideal platform to address competing phases, metallic quantum criticality, and emergent symmetries at the infrared unstable quantum critical points. I will show that the global phase diagram of two-dimensional extended honeycomb-Hubbard model of interacting massless Dirac fermions is governed by altogether five quantum critical points. They display confluence among antiferromagnet, quantum Spin Hall insulator, charge-density-wave, Kekule valence bond solids, and s-wave pairing, for example, and restoration of enlarged symmetry among them. These outcomes will then be substantiated by representative cuts of the global phase diagram in the presence of onsite Hubbard and nearest-neighbor interactions, for example. I will also discuss the role of the long-range tail of the Coulomb interaction on the global phase diagram of this system. |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S43.00010: Local Probes for Charge-Neutral Edge States in Two-Dimensional Quantum Magnets Johannes Knolle, Johannes Feldmeier, Willian Natori, Michael Knap The bulk-boundary correspondence is a defining feature of topological states of matter. However, for quantum magnets such as spin liquids or topological magnon insulators a direct observation of topological surface states has proven challenging because of the charge-neutral character of the excitations. Here we propose spin-polarized scanning tunneling microscopy as a spin-sensitive local probe to provide direct information about charge neutral topological edge states. We show how their signatures, imprinted in the local structure factor, can be extracted by specifically employing the strengths of existing technologies. As our main example, we determine the dynamical spin correlations of the Kitaev honeycomb model with open boundaries. We show that by contrasting conductance measurements of bulk and edge locations, one can extract direct signatures of the existence of fractionalized excitations and non-trivial topology. The broad applicability of this approach is corroborated by a second example of a kagome topological magnon insulator. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S43.00011: Negative electronic compressibility in multi-band 2D electron gases with application to LaAlO3/SrTiO3 Aditi Mahabir, Alexander Balatsky, Jason Haraldsen We investigate the effects of a two-band model in the description of the negative electronic compressibility (NEC) for the two-dimensional electron gas (2DEG). Using a homogeneous 2D interacting electron model, we examine the crossover point of the electronic compressibility of the 2DEG with one and two electron bands and find that the presence of inter-band coupling produces a dramatic decrease in the effective dielectric constant and the critical carrier density of the 2DEG. Furthermore, we investigate how these parameters change with variable effective mass. Additionally, we apply our results to the NEC observed in the 2D electron gas at the interface of LaAlO3/SrTiO3 (LAO/STO) and demonstrate how one can observe effects of inter-band interactions in electronic compressibility. We determine that for the known parameters of LAO/STO, the system may be a realization of two-band 2D electron gas. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S43.00012: Realization of an antiferromagnetic superatomic graphene: Dirac Mott insulator and circular dichroism Hall effect Yinong Zhou, Feng Liu Based on first-principles calculations, we investigate the electronic and topological properties of an antiferromagnetic (AFM) superatomic graphene lattice superimposed on a bipartite honeycomb lattice governed by Lieb’s theorem of itinerant magnetism. It affords a concrete material realization of the AFM honeycomb model with a Dirac Mott insulating state, characterized by a gap opening at the Dirac point due to inversion symmetry breaking by long-range AFM order. The opposite Berry curvatures of the K and K′ valleys induces a circular dichroism (CD) Hall effect. Different from the valley Hall effect that activates only one valley, the CD Hall effect activates carriers from both K and K′ valleys, generating the opposite spin carriers and opposite directions of transversal Hall currents for the left- and right-handed circularly polarized light, respectively. |
Thursday, March 18, 2021 1:54PM - 2:06PM Live |
S43.00013: A fermionic Quantum Monte Carlo study of Twisted Bilayer Graphene Jong Yeon Lee, Johannes Hofmann, Eslam Khalaf, Ashvin Vishwanath, Erez Berg We present a quantum Monte Carlo (QMC) study of twisted bilayer graphene (TBG) near the magic angle at half-filling. Due to its strongly interacting nature as well as topological obstructions for a simple lattice model, an unbiased numerical study of a continuum model of TBG has been a challenging problem. We establish the absence of the sign problem for this model and describe a computationally tractable formulation of this problem. Finally, we will present results from the QMC studies and the phase diagram on tuning physical parameters. |
Thursday, March 18, 2021 2:06PM - 2:18PM Live |
S43.00014: Correlation-driven super Van Hove singularity in slow graphene Baokai Wang, Bahadur Singh, Hsin Lin, Robert Markiewicz, Arun Bansil High-order Van Hove singularities (VHSs) provide a novel mechanism for driving strong electron correlation effects in materials such as the super-metallic state. We show how such VHSs emerge in the paradigmatic family of slow graphenes to produce the excitonic insulator (EI) state. Our systematic analysis reveals a crossover from a weak to a strong electron-correlation regime, which is triggered when velocity of the Dirac carriers is reduced through a renormalization of their bandwidth. The resulting flattening of the edges of the conduction and valence bands yields QΓ = (0, 0) and QM = (π, 0) excitons and produces correlation-driven high-order VHSs with power-law divergences in the density-of-states. Our study indicates that a variety of 2D materials beyond the twisted bilayer graphene would provide viable single-phase material platforms for exploring the physics of high-order VHSs and how these VHSs drive exciting correlation-driven phenomena in quantum matter. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700