Lower Bound to the Entanglement Entropy of the XXZ Spin Ring

Abstract: We study the free XXZ quantum spin model defined on a ring of size $L$ and show that the bipartite entanglement entropy of eigenstates belonging to the first energy band above the vacuum ground state satisfies a logarithmically corrected area law. Along the way, we show a Combes-Thomas estimate for fiber operators which can also be applied to discrete many-particle Schr\"odinger operators on more general translation-invariant graphs.