Dynamics of the vacuum state in a periodically driven Rydberg chain

Mukherjee, B and Sen, A and Sen, D and Sengupta, K (2020) Dynamics of the vacuum state in a periodically driven Rydberg chain. In: Physical Review B, 102 (7).

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Abstract

We study the dynamics of a periodically driven Rydberg chain starting from the state with zero Rydberg excitations (vacuum state denoted by |0)) using a square pulse protocol in the high drive amplitude limit. We show, using exact diagonalization for finite system sizes (L�26), that the Floquet Hamiltonian of the system, within a range of drive frequencies that we chart out, hosts a set of quantum scars that have large overlap with the |0) state. These scars are distinct from their counterparts having high overlap with the maximal Rydberg excitation state (|Z2)); they coexist with the latter class of scars and lead to persistent coherent oscillations of the density-density correlator starting from the |0) state. We also identify special drive frequencies at which the system undergoes perfect dynamic freezing, and we provide an analytic explanation for this phenomenon. Finally, we demonstrate that for a wide range of drive frequencies, the system reaches a steady state with subthermal values of the density-density correlator. The presence of such subthermal steady states, which are absent for dynamics starting from the |Z2) state, imply a weak violation of the eigenstate thermalization hypothesis in finite-sized Rydberg chains distinct from that due to the scar-induced persistent oscillations reported earlier. We conjecture that in the thermodynamic limit, such states may exist as prethermal steady states that show anomalously slow relaxation. We supplement our numerical results by deriving an analytic expression for the Floquet Hamiltonian using a Floquet perturbation theory in the high amplitude limit, which provides an analytic, albeit qualitative, understanding of these phenomena at arbitrary drive frequencies. We discuss experiments that can test our theory. © 2020 American Physical Society.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	The copyright of this article belongs to American Physical Society
Keywords:	Dynamics; Excited states; Hamiltonians; Perturbation techniques, Analytic expressions; Coherent oscillations; Exact diagonalization; Floquet Hamiltonian; High amplitude limit; Perturbation theory; Rydberg excitation; Thermodynamic limits, Quantum theory
Department/Centre:	Division of Physical & Mathematical Sciences > Centre for High Energy Physics Division of Physical & Mathematical Sciences > Physics
Date Deposited:	22 Sep 2020 11:33
Last Modified:	22 Sep 2020 11:33
URI:	http://eprints.iisc.ac.in/id/eprint/66522

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