On entanglement evolution across defects in critical chains

TL;DR

This paper studies how entanglement entropy evolves in critical free-fermion chains after a local quench, revealing that its growth is governed by an effective central charge and varies with initial conditions.

Contribution

It demonstrates that entanglement growth in critical chains with defects is governed by the same effective central charge as in ground states, including for unequal initial fillings.

Findings

Logarithmic entanglement growth governed by effective central charge

Linear entanglement increase for unequal initial fillings

Exact relation between entanglement dynamics and ground-state properties

Abstract

We consider a local quench where two free-fermion half-chains are coupled via a defect. We show that the logarithmic increase of the entanglement entropy is governed by the same effective central charge which appears in the ground-state properties and which is known exactly. For unequal initial filling of the half-chains, we determine the linear increase of the entanglement entropy.