Inverting multiple quantum many-body scars via disorder

Abstract

The recent observations of persistent revivals in the Rydberg atom chain have revealed a weak ergodicity breaking mechanism known as quantum many-body scars, which is typically a collection of states with low entanglement embedded in otherwise thermal spectra. Here, by applying a generic formalism, we propose a direct evolution from the quantum many-body scars to their inverse case and construct multiple inverted quantum many-body scars, i.e., different sets of excited states with volume-law entanglement embedded in a sea of the many-body localized spectrum. When increasing the disorder strength, a tower of exact eigenstates remain intact, acting as conventional quantum many-body scars at weak disorder, and each residing inside narrow energy windows with the emerged inverted quantum many-body scar at strong disorder. Moreover, the strong disorder also induces additional sets of inverted quantum many-body scars with their energies concentrating in the middle of the exact eigenstates. As a result, all the multiple inverted quantum many-body scars are approximately equidistant in energy. We further examine the stability of the conventional and the inverted quantum many-body scars against the external random field. Our findings expand the variety of nonthermal systems and connect the weak ergodicity breaking with the weak violation of many-body localization.

Disorder-tunable entanglement at infinite temperature

“…While the disorder strength was assumed to be sufficiently weak in this work such that the system overall remains chaotic, the versatility of our setup allows direct access to strong ergodicity-breaking regimes, where many-body localization was recently proposed to give rise to "inverted scarring" phenomena (41)(42)(43). More generally, our work bridges the gap between theoretical studies of QMBS, which place the emphasis on exact constructions of scarred eigenstates (16,17), and experimental realizations, e.g., in Rydberg atom arrays (18,19) or optical lattices (21), in which the scarred states are not known exactly [apart from a few exceptions (44)].…”