Effect of Single Impurity on Free Fermion Entanglement Entropy

TL;DR

This paper investigates how a single impurity affects the entanglement entropy in a one-dimensional free Fermi gas, revealing sub-leading contributions that scale inversely with subsystem size, through analytical and numerical methods.

Contribution

It provides the first detailed analysis of impurity-induced sub-leading entanglement entropy corrections in a conformally invariant free fermion system.

Findings

Impurity causes sub-leading entanglement entropy terms.

Corrections scale inversely with subsystem size.

Analytical and numerical results agree on impurity effects.

Abstract

The one-dimensional free Fermi gas is a prototype conformally invariant system, whose entanglement properties are well-understood. In this work, the effects of a single impurity on one dimensional free fermion entanglement entropy are studied both analytically and numerically. Such an impurity represents an exactly marginal perturbation to the bulk conformally invariant fixed point. We find that the impurity leads to sub-leading contributions to the entanglement entropy that scale inversely with the subsystem size. The origin of such contributions are identified.