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 W19: Topology in Dynamical Systems |
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Sponsoring Units: DCMP Chair: Priya Sharma, University of Connecticut Room: Room 211 |
Thursday, March 9, 2023 3:00PM - 3:12PM Author not Attending |
W19.00001: A topological perspective on the steady shift current Aris Alexandradinata Contrary to widespread belief, the intraband Berry phase is irrelevant to the shift component of the bulk photovoltaic current in the steady state. Here, I make the case that topological defects of the interband Berry connection are conducive for a large, steady shift current. |
Thursday, March 9, 2023 3:12PM - 3:24PM |
W19.00002: Berry phase formalism of shift currents and its usage in discovering 3D topological observables: non-E-field-driven transports at topological transitions in insulators/semi-metals. Boqun Song, JIGANG Wang One present-day challenge is that for D-dimensional topological materials its observable’s dimension is d=D-1, known as the principle of bulk-edge correspondence. For the higher-order topological effect, it is D-2, D-3, etc. This limits its detection and usage. In this talk, We present a result about D-dimension topological phase transition (TPT) causing observables of D-dimension. The key to the breakthrough is that without increasing the material dimension, we obtain an “extra” dimension from the time axis. |
Thursday, March 9, 2023 3:24PM - 3:36PM |
W19.00003: Quantum geometry and topological bounds on dissipation in slowly driven quantum systems Iliya Esin, Etienne Lantagne-Hurtubise, Frederik S Nathan, Gil Refael We show that the dissipation of energy in nearly adiabatically driven quantum systems admits a geometric interpretation associated with trajectories on a manifold characterized by the quantum geometry of the problem. This geometric picture allows to devise optimal driving protocols – i.e., minimizing the dissipation rate - for a particular task by following geodesics on the dissipation manifold. Furthermore, the quantum nature of the dissipation manifold implies a relation between the dissipation rate and the Berry curvature of the system. We demonstrate that for a system slowly driven by a two-tone incommensurate drive, the dissipation rate has a lower bound proportional to a topological number describing the energy conversion between the two tones, implying the impossibility of protocols with arbitrarily low dissipation for drives with non-trivial topology. Our results pave the way towards developing optimal driving protocols for topological drives. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W19.00004: Topological invariants of adiabatic cycles in quantum spin systems Ken Shiozaki The Thouless pump is a one-parameter cycle of 1-dimensional gapped quantum systems with U(1) symmetry, which is classified by integers and is physically the pumped charge per cycle. In this talk, we introduce a generalization of the Thouless pump to quantum spin systems in any dimension with any onsite finite group symmetry. We show a simple model with Z2 onsite symmetry and how it is nontrivial via boundary degrees of freedom. Using the injective matrix product state representation, one can construct the topological invariant of adiabatic cycles, similar to the Berry phase. For generic space dimensions, the U(1) phase winding of the group cycle of ground states serves as the topological invariant of adiabatic cycles. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W19.00005: Geometric phases in unitary and non-unitary radical Floquet dynamics Brenden Roberts, Arpit Dua, Sagar Vijay, Ashvin Vishwanath We demonstrate that under the honeycomb Floquet code of Hastings and Haah all trajectories acquire a nontrivial geometric phase, independent of measurement outcomes. This Pancharatnam phase is the Berry phase of a continuous geodesic evolution between individual post-measurement states; however its value is topological, being a consequence of the automorphism. In the particular case of the honeycomb code, such geodesic paths are in the equivalence class of the radical chiral Floquet unitary, a non-equilibrium topological phase that has been deeply explored. In this way, the honeycomb code constitutes a fixed point of the radical chiral Floquet phase. We discuss the implications for stability as well as the boundary signatures of the nontrivial bulk in the code. |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W19.00006: Isotropic modulating Hamiltonian approach to quantum many-body invertible phases Yuan Yao, Masaki Oshikawa, Akira Furusaki Understanding phase diagrams of quantum many-body systems is important in condensed matter physics, but quite often difficult due to complicated interactions. Pumping procedures, e.g., Thouless pumpings1 and its generalizations2,3,4,5, have been used to show the existence of noncontractible loops in the phase diagram of invertible systems --- with a unique gapped ground state on general closed lattices. In this talk, we will discuss how to find and construct isotropic noncontractible (hyper-)spheres in such a phase diagram by modulating Hamiltonians. Our result shows that those noncontractibility or homotopy groups can be related to the classification of invertible phases or the family of Hamiltonians in a one-to-one manner. |
Thursday, March 9, 2023 4:12PM - 4:24PM |
W19.00007: Driven nonhermitian transverse field 1D Ising model: topological edge modes and entanglement scaling Lei Su, Aashish A Clerk, Ivar Martin We study driven nonhermitian transverse field 1D Ising model (complex magnetic field and interactions). We find a mapping between the steady states of this model and the eingenstate order of the corresponding unitary problem, enriched by the complex character of parameters. When boundary conditions are open, the phases are associated with the presence or absence of Majorana modes, which show remarkable robustness to dissipation inherent in the model. We also establish the correspondence between the scaling behavior of entanglement entropy and the character of the complex quasiparticle spectrum. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W19.00008: Phase transitions of wave packet dynamics in disordered non-Hermitian systems Helene Spring, Viktor A Könye, Anton Akhmerov, Ion C Fulga Transport in Hermitian systems is a property of single frequencies due to the conservation of energy. Starting from the works of Hatano and Nelson, phase transitions in disordered non-Hermitian systems are studied using a single-frequency framework. However, energy is not conserved in non-Hermitian systems, and therefore wave packet dynamics in these systems are not described by single energies. In disordered non-Hermitian systems, wave packets with arbitrary initial conditions will converge to the maximally amplified waveform. This waveform can depend discontinuously on the system parameters, and therefore can undergo transitions directly between two distinct propagating phases. Metal-insulator transitions also exist in these systems, but have a different behavior from single-frequency metal-insulator transitions. |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W19.00009: Topologically-protected states and their dynamical influence in structured reservoirs with chiral sublattice symmetry Savannah Garmon We study the interaction of quantum emitters with a structured reservoir (background continuum) that acts as a topological insulator. Specifically, our structured reservoir is formed by a generalization of the Su-Scrieffer-Heeger (SSH) model that is extended to infinity, such that the continuous spectra includes two or more energy bands. In a previous work, we have shown that both localized and anti-localized zero-energy modes can form in the band gap of such systems and that these modes can absorb pairs of other eigenstates to form higher-order exceptional points (EPs) in some circumstances [1]. In the present work, we show that such states exist due to a chiral sublattice symmetry of the model and we examine their influence on quantum emitter state decay in a variety of circumstances. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W19.00010: Nano-infrared imaging of metal insulator transition in few-layer 1T-TaS2 Songtian Sonia Zhang, Anjaly Rajendran, Sanghoon Chae, Shuai Zhang, Tsaichun Pan, James C Hone, Cory R Dean, Dmitri N Basov Among the family of transition metal dichalcogenides (TMD), 1T-TaS2 stands out for several interesting features including a rich charge density wave phase diagram, quantum spin liquid candidacy, and a low temperature Mott insulator phase. Like many TMDs, low-dimensional 1T-TaS2 has exhibited behaviour differing from the bulk. 1T-TaS2 is also known to be air-sensitive, and its properties can be impacted by substrate defects, particularly in the few-layer limit. In this talk, I will present scanning near-field optical microscopy (SNOM) data on a few layer thick microcrystal of 1T-TaS2 that has been encapsulated from both the atmosphere and substrate impurities. By performing a spatial and temperature dependent study, we image the phase transition down to cryogenic temperatures of 50K. In clean regions of the sample, we find an abrupt metal to insulator transition without intermediate phases. A statistical analysis suggests bimodal high and low temperature phases, and that the characteristic phase transition hysteresis is preserved down to a few-layer limit on a local level. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W19.00011: Directional Electrical Conductivity in Oriented Benzotrithiophene COF Thin Films Jonas F Poehls, Laura Frey, Matthias Hennemann, Timothy Clark, Dana D Medina, R. Thomas R Weitz The field of covalent organic frameworks (COFs) - highly ordered, crystalline polymers based on organic building blocks - opened up a pathway to tailor-made organic materials, as the properties of COFs could be widely modified by tuning the chemical properties and geometries of the building blocks. We report the characterization of two novel highly crystalline and porous COFs based on a novel type thiophene-extended benzotrithiophene (BTT) based building block [1]. Both materials were grown as highly oriented, crystalline thin films on various substrates and extensively structurally and electronically characterized. The electronic measurements revealed a strongly directional charge transport in the thin films, which could be explained using classical molecular-dynamics simulations and indicate the future potential of these material. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W19.00012: Self-wrinkling large band-gap insulating nanosheets for graphene sensor applications Paulo Henrique H Michels Brito, Barbara Pacakova, Sergio Hiroshi Toma, Koiti Araki, Josef Breu, Paul Dommrsnes, Jon Otto Fossum Reduced graphene oxide is being used in the graphene/reduced graphene oxide-based sensor. These two-dimensional (2D) materials, when wrinkled, exhibit different electronic properties compared to flat ones. They have been used for gas detection devices, because their sensitivity and recovery ability are much higher than for flat graphene/reduced graphene oxide (G/rGO). One well-known method of wrinkling 2D G/rGO is the deposition over decorated substrates. Various no-up-scalable fabrication methods of decorated surface production have been used, such as lithography, electrodeposition, nanoimprinting, and sputtering. |
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