Critical entanglement of XXZ Heisenberg chains with defects

TL;DR

This paper investigates how a defect in an XXZ Heisenberg chain affects entanglement entropy, revealing a system-size dependent effective central charge that varies across different magnetic regimes.

Contribution

It provides a detailed analysis of entanglement entropy in defective XXZ chains using DMRG, highlighting the variation of the effective central charge with system size and magnetic phase.

Findings

Effective central charge c' varies with system length.

c' approaches 1 in the ferromagnetic phase.

c' approaches 0 in the antiferromagnetic phase.

Abstract

We study the entanglement properties of anisotropic open spin one-half Heisenberg chains with a modified central bond. The entanglement entropy between the two half-chains is calculated with the density-matrix renormalization method (DMRG).We find a logarithmic behaviour with an effective central charge c' varying with the length of the system. It flows to one in the ferromagnetic region and to zero in the antiferromagnetic region of the model. In the XX case it has a non-universal limit and we recover previous results.