Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session YY10: V: Driven Topological Phases, Non-Hermitian Systems and Beyond |
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Sponsoring Units: DCMP Chair: Stewart Barnes, University of Miami Room: Virtual Room 10 |
Wednesday, March 22, 2023 10:00AM - 10:12AM |
YY10.00001: Interaction-Induced Directional Transport on Driven Coupled Chains Helena Drueeke, Dieter Bauer We examine whether interaction between particles may introduce (topologically protected) directional transport in a driven two-particle quantum system. As a simple example, we consider two one-dimensional chains of equal length, each with one particle. The particles are alternatingly driven, however, without a preferred direction. The two particles interact but are restricted to staying on their respective chain. |
Wednesday, March 22, 2023 10:12AM - 10:24AM |
YY10.00002: Symmetry Protected Topological Corner Modes in a Periodically Driven Interacting Spin Lattice Kelvin Koor, Raditya W Bomantara, Leong-Chuan Kwek Periodic driving has a longstanding reputation for generating exotic phases of matter with no static counterparts. In this work we explore the interplay between periodic driving, interaction effects, and Z2 symmetry that leads to the emergence of Floquet symmetry protected second-order topological phases in a simple but insightful two-dimensional spin-1/2 lattice. Through a combination of analytical and numerical treatments, we verify the formation of corner-localized 0 and π modes, i.e., Z2 symmetry broken operators that respectively commute and anticommute with the one-period time evolution operator, as well as establish the topological nature of these modes by demonstrating their presence over a wide range of parameter values and explicitly deriving their associated topological invariants under special conditions. Finally, we also propose a means to detect the signature of these topological modes on superconducting circuit platforms and discuss the effect of imperfections such as perturbations and disorder. |
Wednesday, March 22, 2023 10:24AM - 10:36AM |
YY10.00003: Dynamical construction of higher-order topological systems Arnob K Ghosh We propose a three-step periodic drive protocol to engineer two-dimensional (2D) Floquet quadrupole superconductors and three-dimensional (3D) Floquet octupole superconductors hosting zero-dimensional Majorana corner modes (MCMs), based on unconventional d-wave superconductivity. Remarkably, the driven system conceives four phases with only 0 MCMs, no MCMs, only anomalous π MCMs, and both regular 0 and anomalous π MCMs. To circumvent the subtle issue of characterizing 0 and π MCMs separately, we employ the periodized evolution operator to architect the dynamical invariants, namely quadrupole and octupole motion in 2D and 3D, respectively, that can distinguish different higher-order topological phases unambiguously. Furthermore, we extend our study using the periodic harmonic drive and generalize the definitions of the dynamical quadrupolar moment for this drive. |
Wednesday, March 22, 2023 10:36AM - 10:48AM |
YY10.00004: Topological Thouless pumping in arrays of coupled spin chains Victor M. Bastidas Thouless pumping is a mechanism to perform topologically protected transport that is intimately related to the integer quantum Hall effect. The current of transported particles is proportional to a topological invariant known as the Chern number. Previous works have mainly focus on topological pumping in systems with simple geometries such as linear and square lattices. However, the generalization of topological pumping for more complex geometries remains largely unexplored. In this contribution, we propose a scheme to perform topological pumping in arrays of coupled spin chains [1]. We show that the topological protection allows to transport superpositions through the array against the effect of local imperfections. Our approach will open a new avenue of research to perform transport of correlated excitations with potential applications to quantum technologies and information processing. Our ideas can be implemented in arrays of coupled superconducting devices. |
Wednesday, March 22, 2023 10:48AM - 11:00AM |
YY10.00005: Anomalous Luttinger equivalence between temperature and curved spacetime:From black holes to thermal quenches baptiste bermond In condensed matter, thermal response theory relies on a deep connection |
Wednesday, March 22, 2023 11:00AM - 11:12AM |
YY10.00006: Spatial Profile of Topological Edge States in Periodically Driven Twisted Bilayer Graphene Oliver J Breach, Iliya Esin, Gil Refael Periodic driving with a circularly polarised laser in the mid-IR range is capable of inducing non-trivial topology in twisted bilayer graphene (TBG). Here, we study the spatial profile of chiral edge states that emerge at the boundary between opposite chiralities of the spatially-modulated driving field. We find that at small twist angles, the induced gap is highly renormalized by interlayer coupling, and the resulting edge states have a large spatial width of order 10-100 nm which is in the experimentally detectable range. We establish an analytical model based on a continuum approximation about the Dirac points, which predicts the properties of the edge states as a function of twist angle, driving amplitude, and 'sharpness' of the edge. Surprisingly, we found that despite the decrease in moiré unit cell size, increasing twist angle (above 1.1°) increases the edge state width. We support our analytical predictions by a numerical study based on the Bistritzer-MacDonald continuum model, accounting for the drive through both an effective Hamiltonian and a full Floquet approach. The large size of the edge states may provide a feasible route towards the direct detection of Floquet edge states using time and |
Wednesday, March 22, 2023 11:12AM - 11:24AM |
YY10.00007: Floquet engineering of a model semiconductor by time-resolved ARPES Shaohua Zhou, Changhua Bao, Benshu Fan, Peizhe Tang, Sheng Meng, Wenhui Duan, Shuyun Zhou Time-periodic light field has emerged as a control knob for manipulating quantum states in solid-state materials via hybridization with photondressed Floquet states in the strong coupling limit, dubbed as Floquet engineering. Such interaction leads to tailored properties of quantum materials, for example, modifications of the topological properties of Dirac materials and emergence of Floquet topological insulators. Despite extensive research interests over the past decade, there is no experimental evidence of Floquet engineering of semiconductors, which is a crucial step to extend Floquet engineering to a wide range of solid-state materials. Here, based on time- and angle-resolved photoemission spectroscopy measurements, we report the experimental evidence of Floquet band engineering in a model semiconductor. Floquet sidebands and strong band renormalization are both successfully realized. |
Wednesday, March 22, 2023 11:24AM - 11:36AM |
YY10.00008: Anomalous Transport Induced by Non-Hermitian Anomalous BerryConnection in Non-Hermitian Systems Jionghao Wang Non-Hermitian materials can exhibit not only exotic energy band structures but also an anomalous velocity induced by non-Hermitian anomalous Berry connection as predicted by the semiclassical equations of motion for Bloch electrons. However, it is unclear how the modified semiclassical dynamics modifies transport phenomena. Here, we theoretically demonstrate the emergence of anomalous oscillations driven by either an external dc or acelectric field, which arise from non-Hermitian anomalous Berry connection. Moreover, it is a well-known fact that geometric structures of electric wave functions can only affect the Hall conductivity. However, we are surprised to find a non-Hermitian anomalous Berry connection induced anomalous linear longitudinal conductivity independent of the scattering time. We also show the emergence of a second-order nonlinear longitudinal conductivity induced by non-Hermitian anomalous Berry connection, violating a well-known fact of its absence in a Hermitian system with symmetric energy spectra. These anomalous phenomena are illustrated in a pseudo-Hermitian system with large non-Hermitian anomalous Berry connection. Finally, we propose a practical scheme to realize the anomalous oscillations in an optical system. |
Wednesday, March 22, 2023 11:36AM - 11:48AM Author not Attending |
YY10.00009: Exceptional topological robustness probed by real-time bulk and edge measurements Anh Ho Hoai, Talbot Knighton, Zhe Wu, Vinicio Tarquini, Jian Huang, Loren N Pfeiffer, Ken West Though topology-themed studies are progressing in several aspects, what controls the topological robustness (or fragility) remains an unresolved fundamental question. Studies of the protected edge states so far attribute the variations in the robustness level primarily to the disorder effects. However, the findings cannot address the more general effect of topological breakdowns that necessarily involve the bulk states. Unlike the edge states, probing the bulk excitations is notoriously nontrivial. First, probing an enormous insulator requires an unconventional setup capable of accurately capturing dynamic responses in ultra-high impedance limits. Second, even if an appropriate bulk probe is found, detecting the bulk remains challenging because there exist reconstruction effects possessing random and dynamic features percolating over larger length scales. Here, a new method is demonstrated that enables such a real-time measurement in the integer quantum Hall effect (IQHE) hosted in a Corbino geometry. The extra pair of edge channels are utilized as parallel line probes to the bulk states. This setup allows completely independent measurement of the bulk and edge states so that appropriate sourcing/sensing techniques methods are set up to accurately detect conductors and insulators at the same time. Rendering the IQHE to the verge of a breakdown, accurately measured insulating and conducting responses reveal exceptionally more robust topological protection in a strongly correlated limit than in weakly interacting systems. The cause of the breakdown is identified as back-scatterings arising between dissipationless current paths of opposite chirality facilitated by rare local resonant tunnelings. A unique ``staircase" bulk feature, captured in real-time correspondence with the emergence of edge dissipation and deviation from Hall quantization, indicates a dielectric reconstruction effect influenced by enhanced impurity screening due to strong electron-electron interaction. These findings provide new insight into optimizing topological robustness, as well as pave the road for pursuing instrinic topology in strongly correlated limits. |
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