Entanglement entropy and entanglement witnesses in models of strongly interacting low-dimensional fermions

TL;DR

This paper investigates how entanglement entropy varies across different phases of strongly interacting low-dimensional fermion systems, revealing its dependence on critical points, crossovers, and Hilbert space constraints.

Contribution

It provides a detailed analysis of entanglement entropy in various phases of low-dimensional fermionic models, highlighting its non-thermodynamic nature and relation to quantum criticality.

Findings

Entanglement entropy varies with system parameters and phases.

Enhanced entanglement near quantum critical points in antiferromagnetic insulators.

Spin gaps correlate with increased entanglement at criticality.

Abstract

We calculate the entanglement entropy of strongly correlated low-dimensional fermions in metallic, superfluid and antiferromagnetic insulating phases. The entanglement entropy reflects the degrees of freedom available in each phase for storing and processing information, but is found not to be a state function in the thermodynamic sense. The role of critical points, smooth crossovers and Hilbert space restrictions in shaping the dependence of the entanglement entropy on the system parameters is illustrated for metallic, insulating and superfluid systems. The dependence of the spin susceptibility on entanglement in antiferromagnetic insulators is obtained quantitatively. The opening of spin gaps in antiferromagnetic insulators is associated with enhanced entanglement near quantum critical points.