Block Entanglement Entropy of Ground States with Long-Range Magnetic Order

TL;DR

This paper investigates how the entanglement entropy of ground states with long-range magnetic order scales with block size, revealing a logarithmic growth pattern in both antiferromagnetic and ferromagnetic cases.

Contribution

It extends the calculation of entanglement entropy to ground states with perfect long-range magnetic order, including degenerate states, and analyzes their entropy scaling behavior.

Findings

Entropy grows logarithmically with block size in both cases

Ground state degeneracy affects entanglement entropy calculation

Results have implications for states with general long-range order

Abstract

In this paper we calculate the block entanglement entropies of spin models whose ground states have perfect antiferromagnetic or ferromagnetic long-range order. In the latter case the definition of entanglement entropy is extended to properly take into account the ground state degeneracy. We find in both cases the entropy grows logarithmically with the block size. Implication of our results on states with general long-range order will be discussed.