Local impurities in 2D quantum antiferromagnets

TL;DR

This paper investigates how local impurities like ferromagnetic bonds and impurity spins affect the ground state and local magnetization in 2D quantum antiferromagnets, revealing a local ground state transition and finite magnetization under strong coupling.

Contribution

It introduces an analytic approach and exact diagonalization methods to study the effects of local impurities on 2D quantum antiferromagnets, highlighting a local ground state transition and persistent magnetization.

Findings

Local ground state transition due to impurities.

Finite local magnetization persists even with strong coupling.

Analytic and exact diagonalization methods effectively analyze impurity effects.

Abstract

The two-dimensional quantum Heisenberg antiferromagnet at zero temperature with two kinds of locally frustrating defects - isolated ferromagnetic bonds and impurity spins, is studied. For a quantum spin, coupled antiferromagnetically to the two sublattices, we find a local ground state transition. In the case of a ferromagnetic bond, the local magnetization is found to remain finite even for strong coupling, contrary to previous results, derived within the linear spin-wave approximation. Our results are based on an analytic approach, suitable to treat strong defect-environment interaction, as well as exact diagonalization studies. Technical details and some extension of this work can be found in cond-mat/9712281.