SAMOP 2023 – scientific programme
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A: Fachverband Atomphysik
A 18: Ultra-cold Plasmas and Rydberg Systems I (joint session A/Q)
A 18.1: Talk
Wednesday, March 8, 2023, 14:30–14:45, F303
Topological phases of Rydberg spin excitations in a honeycomb lattice induced by density-dependent Peierls phases — •Simon Ohler1, Maximilian Kiefer-Emmanouilidis1, 2, and Michael Fleischhauer1 — 1University of Kaiserslautern-Landau, D-67663 Kaiserslautern, Germany — 2German Research Centre for Artificial Intelligence, D-67663 Kaiserslautern, Germany
We show that the nonlinear transport of bosonic excitations in a honeycomb lattice of spin-orbit coupled Rydberg atoms gives rise to disordered quantum phases which are topological and candidates for spin liquids. As demonstrated in [Lienhard et al. Phys. Rev. X, 10, 021031 (2020)] the spin-orbit coupling breaks time-reversal and chiral symmetries and leads to a density-dependent complex hopping of the hard-core bosons or equivalently to complex XY spin interactions. Using exact diagonalization (ED) we investigate the phase diagram resulting from the competition between density-dependent and direct transport. In mean-field there is a transition from a quasi-condensate to a 120∘-phase when the complex hopping exceeds the direct one. In the full model a new phase with a finite spin gap emerges close to the mean-field critical point due to quantum fluctuations induced by the density-dependence of the hopping. We show that this phase is a genuine disordered one. It has a large spin chirality and a many-body Chern number C=1, which is robust to disorder. ED simulations of small lattices point to a non-degenerate ground state and thus to a bosonic integer-quantum Hall (BIQH) phase, protected by U(1) symmetry.