Dephasing enhanced spin transport in the ergodic phase of a many-body localizable system

TL;DR

This paper investigates how bulk dephasing influences high-temperature spin transport in a disordered Heisenberg chain, revealing a competition between disorder and dephasing that can enhance transport in the ergodic phase.

Contribution

It uncovers the role of dephasing in modifying spin transport, showing a transition from diffusive to sub-diffusive behavior and identifying conditions for dephasing-enhanced transport.

Findings

Dephasing induces diffusive transport across the system.

A remnant of the diffusive to sub-diffusive transition persists with dephasing.

Competition between disorder and dephasing length scales can enhance transport.

Abstract

We study high temperature spin transport in a disordered Heisenberg chain in the ergodic regime when bulk dephasing is present. We find that while dephasing always renders the transport diffusive, there is nonetheless a remnant of the diffusive to sub-diffusive transition found in a system without dephasing manifested in the behaviour of the diffusion constant with the dephasing strength. By studying finite-size effects we show numerically and theoretically that this feature is caused by the competition between large crossover length scales associated to disorder and dephasing that control the dynamics observed in the thermodynamic limit. We demonstrate that this competition may lead to a dephasing enhanced transport in this model.