Heat transport in the $XXZ$ spin chain: from ballistic to diffusive regimes and dephasing enhancement

TL;DR

This paper investigates heat transport in an XXZ spin chain, revealing how dephasing can induce diffusive behavior in weak interactions and enhance heat current in strongly interacting regimes for small systems.

Contribution

It provides a detailed analysis of how bulk dephasing affects heat transport regimes and demonstrates dephasing-induced enhancement of heat current in certain conditions.

Findings

Dephasing induces diffusive transport in weakly-interacting regimes.

Dephasing decreases heat current in weakly-interacting regimes.

Dephasing can enhance heat current in strongly-interacting regimes for small systems.

Abstract

In this work we study the heat transport in an XXZ spin-1/2 Heisenberg chain with homogeneous magnetic field, incoherently driven out of equilibrium by reservoirs at the boundaries. We focus on the effect of bulk dephasing (energy-dissipative) processes in different parameter regimes of the system. The non-equilibrium steady state of the chain is obtained by simulating its evolution under the corresponding Lindblad master equation, using the time evolving block decimation method. In the absence of dephasing, the heat transport is ballistic for weak interactions, while being diffusive in the strongly-interacting regime, as evidenced by the heat-current scaling with the system size. When bulk dephasing takes place in the system, diffusive transport is induced in the weakly-interacting regime, with the heat current monotonically decreasing with the dephasing rate. In contrast, in the strongly-interacting regime, the heat current can be significantly enhanced by dephasing for systems of small size.