Inverting multiple quantum many-body scars via disorder

TL;DR

This paper explores how disorder can invert quantum many-body scars, transforming low-entanglement states into highly entangled states within localized spectra, revealing new nonthermal phases and connections to many-body localization.

Contribution

It introduces a formalism for transitioning from quantum many-body scars to inverted scars using disorder, demonstrating their coexistence and stability in disordered systems.

Findings

Weak disorder preserves some quantum scars as low-entanglement states.

Strong disorder creates inverted scars with volume-law entanglement.

Multiple inverted scars are approximately equally spaced in energy.

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 generalizing a generic formalism, we propose a direct evolution from the quantum many-body scars to the 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 violation of ergodicity with the weak violation of many-body localization.