Diffusion and Thermalization in a Boundary-Driven Dephasing Model

TL;DR

This paper investigates a boundary-driven fermionic system with dephasing, revealing a crossover from ballistic to diffusive transport, and characterizing how bulk thermalization coexists with boundary-induced non-equilibrium features.

Contribution

It provides an exact analysis of spectral and occupation properties in a Lindblad model with dephasing, highlighting the interplay between thermalization and boundary-driven non-equilibrium states.

Findings

Bulk distribution becomes flat, indicating infinite temperature thermalization.

Transport exhibits a crossover from ballistic to diffusive behavior.

Boundary regions show strong non-equilibrium features.

Abstract

We study a model of non-interacting spinless fermions coupled to local dephasing and boundary drive and described within a Lindblad master equation. The model features an interplay between infinite temperature thermalization due to bulk dephasing and a non-equilibrium stationary state due to the boundary drive and dissipation. We revisit the linear and non-linear transport properties of the model, featuring a crossover from ballistic to diffusive scaling, and compute the spectral and occupation properties encoded in the single particle Green's functions, that we compute exactly using the Lindblad equations of motion in spite of the \emph{interacting} nature of the dephasing term. We show that the distribution function in the bulk of the system becomes frequency independent and flat, consistent with infinite temperature thermalization, while near the boundaries it retains strong non-equilibrium features that reflect the continuous injection and depletion of particles due to driving and dissipation.