# Analytical results for the entanglement Hamiltonian of a free-fermion chain

## TL;DR

This paper derives explicit analytical expressions for the entanglement Hamiltonian of a free-fermion chain, revealing persistent deviations from conformal predictions even at large system sizes.

## Contribution

It provides the first explicit large-$N$ expressions for the entanglement Hamiltonian in free-fermion chains at arbitrary filling.

## Key findings

- Analytical expressions match numerical results
- Deviations from conformal field theory persist at large $N$
- Explicit formulas relate to a commuting operator

## Abstract

We study the ground-state entanglement Hamiltonian for an interval of $N$ sites in a free-fermion chain with arbitrary filling. By relating it to a commuting operator, we find explicit expressions for its matrix elements in the large-$N$ limit. The results agree with numerical calculations and show that deviations from the conformal prediction persist even for large systems.