Discrete time crystals enforced by Floquet-Bloch scars

TL;DR

This paper introduces Floquet-Bloch scars, a new class of quantum scars in driven systems, which enforce discrete time crystal oscillations and are protected by spatiotemporal symmetries, verified through analytical solutions and numerical models.

Contribution

It identifies and analytically characterizes Floquet-Bloch scars, revealing their role in stabilizing discrete time crystal behavior in translation-invariant systems.

Findings

Floquet-Bloch scars enforce rigid DTC oscillations

Spectral pairing is unique to Floquet systems with strong interactions

Numerical verification in a kagome lattice model

Abstract

We analytically identify a new class of quantum scars protected by spatiotemporal translation symmetries, dubbed Floquet-Bloch scars. They distinguish from previous (quasi-)static scars by a rigid spectral pairing only possible in Floquet systems, where strong interaction and drivings equalize the quasienergy corrections to all scars and maintain their spectral spacings against generic bilinear perturbations. Scars then enforce the spatial localization and rigid discrete time crystal (DTC) oscillations as verified numerically in a trimerized kagome lattice model relevant to recent cold atom experiments. Our analytical solutions offer a potential scheme to understand the mechanisms for more generic translation-invariant DTCs.