System-bath entanglement during Markovian relaxation of a fermionic impurity

TL;DR

This paper explores how transient entanglement between a fermionic impurity and its environment arises during thermalization, even under weak coupling, and relates it to the underlying unitary dynamics.

Contribution

It reveals the existence of transient system-bath entanglement during Markovian relaxation in fermionic systems and links it to the unitary nature of the dynamics.

Findings

Transient entanglement occurs even in weak coupling regimes.

Entanglement magnitude depends on initial state purity.

Entanglement vanishes at long times, persists over relaxation timescales.

Abstract

We investigate the dynamics of entanglement between the system and the environment during thermalization of a noninteracting fermionic impurity coupled to a fermionic thermal bath. We show that transient entanglement can be observed even in the weak coupling regime, when the reduced dynamics and thermodynamics of the system can be well described by an effectively classical and Markovian master equation for the state populations. This entanglement vanishes for long times, but is preserved over timescales comparable to the relaxation time. Its magnitude depends only weakly on the system-environment coupling but instead strongly on the purity of the initial state of the system. We relate the presence of such transient entanglement to the unitary character of the system-bath dynamics underlying the reduced Markovian description.