Inhomogeneous quantum antiferromagnetism on periodic lattices

TL;DR

This paper investigates how local lattice structure variations affect quantum antiferromagnetic order, revealing that higher coordination sites can have lower magnetic moments, challenging common assumptions.

Contribution

It introduces a detailed analysis of inhomogeneous antiferromagnetism on various bipartite lattices using spin wave theory and Monte Carlo simulations, highlighting the counterintuitive relationship between coordination and magnetic order.

Findings

High coordination sites have lower ordered moments.

Local bond expectations vary significantly across lattices.

The Heisenberg star model offers analytical insights.

Abstract

We study quantum antiferromagnets on two-dimensional bipartite lattices. We focus on local variations in the properties of the ordered phase which arise due to the presence of inequivalent sites or bonds in the lattice structure, using linear spin wave theory and quantum Monte Carlo methods. Our primary finding is that sites with a high coordination tend to have a low ordered moment, at odds with the simple intuition of high coordination favoring more robust Neel ordering. The lattices considered are the dice lattice, which is dual to the kagome, the CaVO lattice, an Archimedean lattice with two inequivalent bonds, and the crown lattice, a tiling of squares and rhombi with a greater variety of local environments. We present results for the onsite magnetizations and local bond expectation values for the spin-1/2 Heisenberg model on these lattices, and discuss the exactly soluble model of a Heisenberg star, which provides a simple analytical framework for understanding our lattice studies.