Effects of edges in spin-1/2 bond-alternating Heisenberg chains: Matrix-product variational approach

TL;DR

This paper uses a matrix-product variational approach to study edge effects in spin-1/2 bond-alternating Heisenberg chains, revealing how anisotropy influences phase diagrams and induces unique edge states.

Contribution

It introduces a variational method that effectively captures phase behavior and edge states in anisotropic spin chains with minimal parameters.

Findings

Reproduces complex phase diagram with two variational parameters.

Shows anisotropy significantly affects ferromagnetic coupling.

Identifies novel edge states specific to spin-1/2 chains.

Abstract

We make a matrix-product variational approach to spin-1/2 ferromagnetic-antiferromagnetic bond-alternating chains with anisotropy on their ferromagnetic bonds, especially under the open boundary condition. The rich phase diagram containing the Haldane, large-D, and two types of Neel phases is well reproduced with only two variational parameters. The on-bond anisotropy has a significant effect on the ferromagnetic coupling between neighboring spins and induces novel edge states peculiar to spin-1/2 chains.