Anomalous transport in the kinetically constrained quantum East-West model

TL;DR

This paper investigates a kinetically constrained quantum model, revealing diverse transport behaviors from localization to ballistic motion, and uncovers signs of quantum many-body scars and potential anomalous infinite-temperature dynamics.

Contribution

It introduces a reflection symmetry-breaking parameter in a quantum East-West model, showing its impact on transport and revealing signs of quantum many-body scars.

Findings

Domain wall states exhibit localization to ballistic transport.

Infinite-temperature dynamics appear diffusive but show asymmetry in the structure factor.

Presence of low-entangled eigenstates indicating quantum many-body scars.

Abstract

We study a chaotic particle-conserving kinetically constrained model, with a single parameter which allows us to break reflection symmetry. Through extensive numerical simulations we find that the domain wall state shows a variety of dynamical behaviors from localization all the way to ballistic transport, depending on the value of the reflection breaking parameter. Surprisingly, such anomalous behavior is not mirrored in infinite-temperature dynamics, which appear to scale diffusively, in line with expectations for generic interacting models. However, studying the particle density gradient, we show that the lack of reflection symmetry affects infinite-temperature dynamics, resulting in an asymmetric dynamical structure factor. This is in disagreement with normal diffusion and suggests that the model may also exhibit anomalous dynamics at infinite temperature in the thermodynamic limit. Finally, we observe low-entangled eigenstates in the spectrum of the model, a telltale sign of quantum many body scars.