Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 67, Number 7
Monday–Friday, May 30–June 3 2022; Orlando, Florida
Session Q02: Focus Session: Dynamical Gauge Fields in AMO SystemsFocus Live Streamed

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Chair: Shraddha Agrawal, UIUC Room: Grand Ballroom A 
Thursday, June 2, 2022 8:00AM  8:30AM 
Q02.00001: Realising a onedimensional topological gauge theory in an optically dressed BoseEinstein condensate Invited Speaker: Leticia Tarruell Topological gauge theories describe the low energy properties of certain strongly correlated quantum systems through effective weakly interacting models. A prime example is the ChernSimons theory of fractional quantum Hall states, where the emergence of anyonic excitations is explained by the coupling between weakly interacting matter particles and a densitydependent gauge field. While in traditional solidstate platforms such gauge theories are only convenient theoretical constructions, experimental atomic systems enable their direct implementation and are expected to provide a fertile playground to investigate their phenomenology without the need for strong interactions. In my talk, I will report on the first quantum simulation of a topological gauge theory by realising a onedimensional reduction of the ChernSimons theory (the chiral BF theory) in a BoseEinstein condensate. Using the local conservation laws of the theory, we eliminate the gauge degrees of freedom in favour of chiral matter interactions, which we engineer by synthesising optically dressed atomic states with momentumdependent scattering properties. We explore the key properties of the chiral BF theory: the formation of chiral solitons  selfbound states of the matter field that only exist for one propagation direction  and the emergence of an electric field generated by the system itself. Our results expand the scope of quantum simulation to topological gauge theories and pave the way towards implementing analogous field theories in higher dimensions. 
Thursday, June 2, 2022 8:30AM  9:00AM 
Q02.00002: Wavepacket dynamics in Floquet topological systems Invited Speaker: Monika Aidelsburger Periodic driving, also known as Floquet engineering, is a powerful experimental technique to realize topological lattice models with ultracold atoms in optical lattices. Here, we report on the realization of distinct topological models using periodic driving with bosonic atoms in a hexagonal optical lattice. We probe different topological regimes using a combination of spectroscopic measurements and local Hall deflections, thereby revealing the topological invariants that characterize the different topological regimes. Depending on the modulation parameters, we show that genuine outofequilibrium Floquet topological systems can be realized without any static analogue. These systems are characterized by a generalized bulkboundary correspondence, which can support topological edge modes even if the Chern numbers of all bulk bands vanish. We reveal this connection by preparing localized wavepackets at the edge of the systems, which directly signals the presence of topological edge modes. 
Thursday, June 2, 2022 9:00AM  9:12AM 
Q02.00003: Exploring Phase Diagrams of 1D Z_{2} LatticeGauge Theory with Dynamical Matter Matjaz Kebric, Luca Barbiero, Umberto Borla, Sergej Moroz, Ulrich J Schollwoeck, Fabian Grusdt Here, we study a onedimensional latticegauge theory model where dynamical charges are coupled to gauge fields. Such models exhibit confinement and can be realized with modern quantum simulators. By adding nearestneighbor interactions we uncover interesting phase transitions to different Mott states, which are strongly related to the filling. Remarkably, the confining electric field stabilizes a Mott state at the filling of n = 2/3 and destabilizes it for filling n = 1/2. On the other hand, adding superconducting terms instead of the nearestneighbor interactions results in trivial to nontrivial topological transitions, which resemble behavior of the Kitaev chain. In our work we rely on the combination of the numerical DMRG calculations and analytical techniques, which are tractable for specific parameter values and limits. We also develop an effective meanfield theory model of our problem. This simple meanfield model correctly resembles the main features of the original model and offers deeper physical insights. Finally, we also discuss possible experimental realizations with quantum gases in optical lattices. 
Thursday, June 2, 2022 9:12AM  9:24AM 
Q02.00004: Emergent Z_{2} gauge theories and topological excitations in Rydberg quantum simulators Rhine Samajdar, Darshan G Joshi, Yanting Teng, Subir Sachdev Strongly interacting arrays of Rydberg atoms provide versatile platforms for exploring exotic manybody phases and dynamics of correlated quantum systems. Motivated by recent experimental advances, we theoretically investigate the quantum phases that can be realized by such Rydberg atom simulators in two dimensions. We show that the combination of Rydberg interactions and appropriate lattice geometries naturally leads to emergent Z_{2} gauge theories endowed with matter fields. Based on this mapping, we demonstrate how Rydberg platforms can be used to realize topological spin liquid states based solely on their native van der Waals interactions. We also discuss the nature of the fractionalized excitations of two distinct classes of such Z_{2} quantum spin liquid states using both fermionic and bosonic parton theories and illustrate their rich interplay with proximate solid phases. 
Thursday, June 2, 2022 9:24AM  9:36AM 
Q02.00005: Topological quantum Spin Liquid in a hexagonal Lattice of Rydberg Atoms with densitydependent Peierls Phases Simon Ohler, Michael Fleischhauer, Maximilian KieferEmmanouilidis We show that the nonlinear transport of bosonic excitations in a twodimensional honeycomb lattice of spinorbit coupled Rydberg atoms gives rise to disordered quantum phases which are candidates for topological quantum spin liquids. As recently demonstrated in [Lienhard et al., Phys. Rev. X, 10, 021031 (2020)] the spinorbit coupling breaks timereversal and chiral symmetries and leads to a tunable densitydependent complex hopping of the hardcore bosons or equivalently to complex XY spin interactions. We numerically investigate the phase diagram resulting from the competition between densitydependent and direct transport terms. In the regime where the two terms are comparable, we find a disordered quantum state that is absent in a meanfield description. This phase is characterized by a finite spingap, a large spin chirality as well as a manybody Chern number C=1. We therefore identify this phase as a topological spin liquid. 
Thursday, June 2, 2022 9:36AM  9:48AM 
Q02.00006: Observing dynamical currents in a nonHermitian momentum lattice Fabian Finger, Rodrigo RosaMedina, Francesco Ferri, Nishant Dogra, Katrin Kroeger, Rui Lin, Ramasubramanian Chitra, Tobias Donner, Tilman Esslinger Dynamic transients are a natural ingredient of nonequilibrium quantum systems. A paradigmatic example is Dicke superradiance, describing the collectively enhanced population inversion of an ensemble of twolevel atoms coupled to a single mode of light. 
Thursday, June 2, 2022 9:48AM  10:00AM 
Q02.00007: Resonant dynamics of fermions in synthetic flux ladders with strong SU(n) interactions Mikhail Mamaev, Bhuvanesh Sundar, Thomas Bilitewski, Ana Maria Rey We theoretically study the dynamics of strongly interacting fermionic alkaline earth atoms with n internal levels in an optical lattice. When treating the internal flavors as a synthetic dimension, the system realizes a synthetic ladder structure. We use laser driving to couple the internal levels and induce an effective magnetic flux piercing the ladder. The system dynamically generates chiral spin currents in response to the flux. While strong interactions with one atom per site tend to inhibit motion, we show that transport is enhanced at special integer and fractional ratios of the driving and interaction strength, reminiscent of the enhancement of longitudinal conductivity in the fractional quantum Hall effect. At these resonant points, tunneling is induced by multibody resonances that are enabled by the flux. For some resonances the particle transport approaches that of an effectively noninteracting system, while other resonances yield nonthermal behavior due to nontrivial kinetic constraints upon the motion. Our results showcase the plethora of complex dynamical phenomena that strongly interacting SU(n) fermions exhibit in the presence of an effective magnetic flux, many of which can manifest on timescales well within reach of currentgeneration experiments. 
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