Edge effects in the two-dimensional spin-1/2 Heisenberg antiferromagnet

TL;DR

This study uses quantum Monte Carlo simulations to explore how free edges influence magnetic properties in a two-dimensional spin-1/2 Heisenberg antiferromagnet, revealing counter-intuitive edge effects on susceptibility.

Contribution

It demonstrates the contrasting effects of smooth and rough edges on magnetic response, highlighting the role of local correlations and sublattice imbalance.

Findings

Edge susceptibility is smaller than bulk susceptibility.

Enhanced antiferromagnetic correlations near smooth edges.

Rough edges significantly increase susceptibility due to sublattice imbalance.

Abstract

We use quantum Monte Carlo simulations to study effects of free edges in the two-dimensional spin-1/2 Heisenberg antiferromagnet. We find that the magnetic response of an edge is smaller than the bulk susceptibility. This counter-intuitive quantum effect can be traced to enhanced antiferromagnetic nearest-neighbor spin correlations, i.e., tendency to local singlet formation, at and close to the edge. These correlations form a comb-like pattern, which can be reproduced with a simple variational valence-bond state. We also study rough edges, and find that these instead significantly enhance the susceptibility, due to local sublattice imbalance impeding singlet formation.