Classical and quantum two-dimensional anisotropic Heisenberg antiferromagnets

TL;DR

This paper investigates classical and quantum two-dimensional anisotropic Heisenberg antiferromagnets on a square lattice, analyzing phase transitions, structures, and fluctuations using Monte Carlo methods.

Contribution

It provides a detailed comparison of classical and quantum models, examining phase transition scenarios and low-temperature structures with Monte Carlo simulations.

Findings

Classical model shows biconical structures and low-temperature fluctuations.

Quantum model's first-order transition scenario is critically examined.

Identification of critical and tricritical points in the phase diagram.

Abstract

The classical and the quantum, spin $S=1/2, versions of the uniaxially anisotropic Heisenberg antiferromagnet on a square lattice in a field parallel to the easy axis are studied using Monte Carlo techniques. For the classical version, attention is drawn to biconical structures and fluctuations at low temperatures in the transition region between the antiferromagnetic and spin-flop phases. For the quantum version, the previously proposed scenario of a first-order transition between the antiferromagnetic and spin-flop phases with a critical endpoint and a tricritical point is scrutinized.