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arXiv · 2204.08047

Weak ergodicity breaking in Josephson-junction arrays

Angelo Russomanno·Michele Fava·Rosario Fazio
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Abstract

We study the quantum dynamics of Josephson junction arrays. We find isolated groups of low-entanglement eigenstates, that persist even when the Josephson interaction is strong enough to destroy the organization of the spectrum in multiplets, and a perturbative description is no longer possible. These eigenstates provide a weak ergodicity breaking, and are reminiscent of the quantum scars. Due to the presence of these eigenstates, initializing with a charge-density-wave state, the system does not thermalize and the charge-density-wave order persists for long times. Considering global ergodicity probes, we find that the system tends towards more ergodicity for increasing system size: The parameter range where the bulk of the eigenstates look nonergodic shrinks for increasing system size. We study two geometries, a one-dimensional chain and a two-leg ladder. In the latter case, adding a magnetic flux makes the system more ergodic.

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Angelo Russomanno, Michele Fava, Rosario Fazio. 2022-04-17. Weak ergodicity breaking in Josephson-junction arrays. https://doi.org/10.1103/physrevb.106.035123

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