Hierarchical single-ion anisotropies in spin-1 Heisenberg antiferromagnets on the honeycomb lattice

TL;DR

This study investigates the thermal behavior and phase transitions of spin-1 Heisenberg antiferromagnets on a honeycomb lattice with anisotropies, using quantum Monte Carlo simulations to connect theoretical models with experimental neutron scattering data.

Contribution

It provides a detailed analysis of easy-plane and easy-axis anisotropies in spin-1 systems, highlighting the persistence of easy-plane physics near phase transitions despite additional anisotropies.

Findings

Correlation length scaling near phase transition analyzed

Easy-plane physics accessible above critical temperature

Quantum Monte Carlo simulations match experimental observations

Abstract

We examine the thermal properties of the spin-1 Heisenberg antiferromagnet on the honeycomb lattice in the presence of an easy-plane single-ion anisotropy as well as the effects of an additional weak in-plane easy-axis anisotropy. In particular, using large-scale quantum Monte Carlo simulations, we analyze the scaling of the correlation length near the thermal phase transition into the ordered phase. This allows us to quantify the temperature regime above the critical point in which -- in spite of the additional in-plane easy-axis anisotropy -- characteristic easy-plane physics, such as near a Berezinskii-Kosterlitz-Thouless transition, can still be accessed. Our theoretical analysis is motivated by recent neutron scattering studies of the spin-1 compound BaNi${}_2$V${}_2$O${}_8$ in particular, and it addresses basic quantum spin models for generic spin-1 systems with weak anisotropies, which we probe over the full range of experimentally relevant correlation length scales.