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 M66: Topological States in AMO Systems II |
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Sponsoring Units: DAMOP Chair: Nathan Harshman, American University Room: Room 413 |
Wednesday, March 8, 2023 8:00AM - 8:12AM |
M66.00001: An emergent topological pump driven by dissipation in a quantum gas Alexander Baumgärtner, Davide Dreon, Simon E Hertlein, Tobias Donner, Tilman Esslinger The time evolution of a driven quantum system can be strongly affected by dissipation. Although this mainly implies that the system relaxes to a steady state, in some cases it can lead to the appearance of new phases and trigger emergent dynamics. In our experiment, we study a Bose-?Einstein condensate dispersively coupled to a high finesse optical resonator. The cavity is populated by scattering photons from a transverse drive illuminating the atoms. The sum of the drive and the self-?consistent intracavity field provides a lattice potential. When the dissipation via cavity dissipation and the coherent timescales are comparable, we find a regime of persistent oscillations where the cavity field does not reach a steady state. In this regime the atoms experience a potential that periodically deforms itself, even without providing an external time dependent drive. Eventually, the dynamic lattice triggers a topological pumping mechanism. We show complementary measurements of the light field and of the atomic transport, proving the connection between the emergent non-?stationarity and the topological pump. |
Wednesday, March 8, 2023 8:12AM - 8:24AM |
M66.00002: Splitting of topological charge pumping in an interacting two-component fermionic Rice-Mele Hubbard model Eric Bertok, Fabian Heidrich-Meisner, Armando A Aligia A Thouless pump transports an integer amount of charge when pumping adiabatically around a singularity. We study the splitting of such a critical point into two separate critical points by adding a Hubbard interaction. Furthermore, we consider extensions to a spinful Rice-Mele model, namely a staggered magnetic field or an Ising-type spin coupling, further reducing the spin symmetry. The resulting models additionally allow for the transport of a single charge in a two-component system of spinful fermions, whereas in the absence of interactions, zero or two charges are pumped. In the SU(2)-symmetric case, the ionic Hubbard model is visited once along pump cycles that enclose a single singularity. Adding a staggered magnetic field additionally transports an integer amount of spin while the Ising term realizes a pure charge pump. We employ real-time simulations in finite and infinite systems to calculate the adiabatic charge and spin transport, complemented by the analysis of gaps and the many-body polarization to confirm the adiabatic nature of the pump. The resulting charge pumps are expected to be measurable in finite-pumping speed experiments in ultra-cold atomic gases, for which the SU(2) invariant version is the most promising path. We discuss the implications of our results for a related quantum-gas experiment by Walter et al. [arXiv:2204.06561]. |
Wednesday, March 8, 2023 8:24AM - 8:36AM |
M66.00003: Topological Pumping in Optical Quasicrystals Emmanuel Gottlob, Dan Borgnia, Robert-Jan Slager, Ulrich Schneider Cold atoms have become a rich platform for realising topological phases of matter, characterised by finite Chern numbers. In particular, quasiperiodic lattices can exhibit up to infinite Chern numbers, inherited from higher-dimensional parent Hamiltonians. Here, we design an experimentally realizable pumping protocol for optical quasicrystals that leads to bulk currents of topological nature, and harness it to measure the hierarchy of increasing Chern numbers. Expanding the configuration space representation developed in [1], we offer a simple explanation of the fractal energy spectrum based on resonances between increasingly distant sites as well as a general way of understanding the adiabatic pumping of optical quasicrystals. The pumping protocol is illustrated in the case of the one-dimensional Aubry-André model, but is general and applicable for different quasiperiodic lattices, and higher dimensions. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M66.00004: Design of Topological Structures with desired-shape mid-gap state Elnaz Hamdarsi, Hamidreza Ramezani Topological systems with their robust features are of interest in different fields including electronics, acoustics, and photonics. Systems with non-trivial topological configurations are the host of the so-called edge modes with energy eigenfrequency lying at the center of the gap and are protected by the symmetries of the structure. The eigenstates associated with these mid-gap modes are exponentially localized at the boundaries. For practical applications, it is of great interest to design systems that have a protected state not necessarily squeezed towards the edges, and in some cases, it is crucial to have it as a distributed state. Here, by inverse-design programming, we propose a general approach allowing us to generate structures with non-trivial symmetry that have a mid-gap state with the desired shape, which is not restricted to the edge. Although the symmetry in the engineered structure is not obvious, the energy eigenfrequency associated with the mid-gap state in any shape of the distribution is robust against structural imperfections. We demonstrate several examples in 1D and 2D lattices allowing the observation of tunable localization of the mid-gap state and transformed edge state to an extended state. Our work paves the way for new applications of topological effects such as imaging and far-field topological sensing. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M66.00005: Simulating traid anyons with bosons hopping on a lattice Nathan L Harshman, Sebastian Nagies, Botao Wang, Adam C Knapp, André Eckardt We show that, via something like a Jordan-Wigner transform, traid statistics can be engineered into bosons hopping on a lattice with Peierls-type phases, and we consider which observable signatures of this lattice model would reveal the unconventional topological exchange statistics of traid anyons. Traid anyons are indistinguishable particles in one dimension with topological exchange statistics. Following the approach of Leinaas and Myrheim, traid statistics arise from quantizing the configuration space of indistinguishable particles in one dimension with three-body coincidences removed, in the same way that braid statistics follow from quantizing the configuration space of indistinguishable particles in two dimensions with two-body coincidences removed. For abelian traid anyons, when adjacent particles are exchanged, the state transforms as though they were either bosons or fermions. However, the Yang-Baxter relation does not hold, and the transformation induced by the exchange of non-adjacent particles depends on the path taken by the exchange. We show how the lattice model simulates these unconventional statistics by engineering fluxes through loops in discrete configuration space that mimic the topology of the continuum model. Satisfyingly, the continuum limit of the lattice traid model corresponds to bosons with contact interactions that depend on the relative position of the particles and the specific choice of abelian traid representation being simulated. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M66.00006: Non-Hermitian Hopf-Bundle Skin Effects in Electric Circuits Yung Kim, Hee Chul Park, Minwook Kyung, Kyungmin Lee, Moon Jip Park, Bumki Min For matters describable with line and loop excitations, a topological phase can be classified by a linking and braiding structure. Recently, it was proven that the topological phase of one dimensional non-Hermitian system can be characterized by winding and braiding of complex eigenenergy strings. While nontrivial winding of complex eigenenergy strings has recently been demonstrated in a one-synthetic-dimensional photonic system, a topological phase transition and its corresponding physical manifestation in real and momentum spaces have not been visualized yet. Moreover, in higher spatial dimensions, it is found that every string in space can be mutually linked by all other strings, exhibiting a more intricate linking structure. A non-Hermitian Hopf bundle, as such a phase of linked strings, has not been experimentally observed yet. Here, we report the visualization of linking and unlinking of the Hopf bundle in momentum space of a two-dimensional non-Hermitian circuit by introducing an eigenspinor string. We observe that the eigenspinor strings take the form of the nontrivial Hopf bundle in the topological phase. Furthermore, we discover the bulk-boundary correspondence between the nontrivial Hopf-bundle in momentum space and a higher-order skin defect mode in real space. By utilizing controllable capacitance switching, we experimentally confirm the bulk-boundary correspondence by explicitly imaging linking and unlinking topological transitions of the Hopf bundle in momentum space. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M66.00007: Dipolar Chiral Spin Liquids on stretched Kagome lattices Francisco Machado, Sabrina Chern, Michael P Zaletel, Norman Y Yao The interplay between classical frustration and quantum fluctuations in spin systems can lead to spin liquid states---seemingly featureless ground states that exhibit exotic properties such as long-range entanglement and fractionalized excitations. The recent development of highly controllable and coherent quantum simulators offers the tantalizing opportunity to realize and probe such states. In this talk, we demonstrate how the fine-tuned control over geometry can stabilize a chiral spin liquid (CSL) state. Using large scale tensor network calculations, we study a stretched (i.e. breathing) perturbation of a Kagome lattice of long-range dipolar interacting spins, and map out the associated phase diagram. We find a large region where the ground state is a gapped chiral spin liquid that spontaneously breaks time-reversal symmetry and hosts gapless edge modes. We conclude by discussing paths to generating such states in the context of Rydberg tweezer array experiments. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M66.00008: Wave-packet dynamics and edge-state transport in anomalous Floquet topological phases Miguel Mart?nez, Nur Unal The topological characterisation of periodically driven Floquet systems goes beyond equilibrium classification schemes, offering anomalous topological phases without static counterparts. In recent years, the possibility of obtaining chiral edge modes even for bands with vanishing Chern number has attracted a lot of attention both theoretically and experimentally. We here consider a periodically driven honeycomb lattice and provide general phase diagrams for experimentally relevant driving protocols. We reveal yet another type of anomalous topological phase where quasienergy gaps harbour edge states with opposite chirality and investigate wave packet dynamics in different anomalous phases. Focusing on distinct dynamics, we analyse transport properties in relation to each other by comparing various Floquet spectra featuring topological edge states of different characters. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M66.00009: Degenerate Multimode Cavities for Topological Quantum Optics with Rydberg Polaritons Lukas Palm, Matthew Jaffe, Claire Baum, Jonathan Simon Realizing fractional Quantum Hall states in quantum simulation experiments is a long-standing goal on the way to understanding and harnessing topological states of matter. Initial progress has been demonstrated with our realization of a two-photon Laughlin state [1] and recently the demonstration of a two-atom Laughlin state in an optical lattice [2], stimulating the quest to prepare bigger systems where true many-body properties like anyonic quasi particles become accessible. Our hybrid platform uses cavity Rydberg polaritons, quasiparticles of an optical cavity photon hybridized with an interacting atomic Rydberg excitation, to create interactions and artificial gauge fields for light. We will present our new, aspheric lens based degenerate multimode cavity that will allow approaching mesoscopic system sizes, and first experimental results using this platform on the way to larger Quantum Hall states. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M66.00010: Quantum Geometry of the Chirality Induced Spin Selectivity Effect Smita Rajan, Karpur Shukla, Jimmy Xu Chirality underpins a vast array of physical systems, providing a degree of freedom that may often be hidden in plain sight but can give rise to exotic phenomena. One such effect which has garnered growing interest is the chirality-induced spin selectivity (CISS) in which ordered films of chiral molecules act as filters for electron spin, with substantial spin-dependent charge separation being realized. In solid-state systems, topological phases of matter arise from strong spin-orbit interactions, due to electron interactions with heavy lattice ions. The CISS effect in molecules exhibits several hallmarks of topological insulators—spin-dependent transport, spin-locked states, and a nontrivial spin-orbit coupling. This reasoning is enhanced by the discovery of an orbital texture in the band structure of DNA-like molecules. As such, it seems critical to understand whether the spin-polarization from the CISS effect is due to a topologically nontrivial quantum geometry. Our approach involves examining nonrelativistic electrons moving along a helical path, under the effect of a Rashba-like spin-orbit coupling, a constant Zeeman field, and a dipole potential. Using the properties of the CISS Hamiltonian, we compute the non-abelian Berry phase and Chern number for the eigenstates of the Hamiltonian. Topological classification of chiral molecules potentially gives rise to novel exploitation of the CISS effect, expanding the developing field of spintronics into molecular materials. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M66.00011: Vison excitations in Rydberg atom arrays Yanting Teng, Rhine Samajdar, Darshan G Joshi, Subir Sachdev Programmable Rydberg atom arrays have emerged as a powerful quantum |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M66.00012: Loop-hole free electric Aharonov-Bohm effect Michael E Tobar, Douglas A Singleton, Raymond Y Chiao, Harold Hart, Nader (Nathan) Inan, Jay E Sharping, Michael Scheibner We present a loop-hole free version of the electric Aharonov-Bohm effect where the quantum system, which picks up the Aharonov-Bohm phase is confined to a region where only the scalar potential is non-zero. At the same time, the electric and magnetic fields in this region are strictly zero for the entire period of the experiment. In contrast to the usual vector Aharonov-Bohm effect, where a quantum system (usually a charged particle) moves in a static background, vector potential, here the quantum system is a two-level system enclosed by a Faraday cage, which picks up the Aharonov-Bohm phase when at rest with respect to the lab frame, while the uniform scalar potential is varied with time. |
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