Effects of an external magnetic field on the gaps and quantum corrections in an ordered Heisenberg antiferromagnet with Dzyaloshinskii-Moriya anisotropy

TL;DR

This paper investigates how an external magnetic field influences the quantum properties and excitation gaps of a 2D Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interaction, revealing non-analytic behaviors and the suppression of quantum fluctuations.

Contribution

It provides a detailed analysis of the field-dependent quantum corrections and excitation gaps in a Heisenberg antiferromagnet with DM anisotropy, highlighting the suppression of quantum fluctuations by the DM interaction.

Findings

Unusual field-evolution of spin-wave gaps.

Non-analytic dependencies of quantum corrections on H and D.

DM interaction suppresses quantum fluctuations, favoring classical ground states.

Abstract

We study the effects of external magnetic field on the properties of an ordered Heisenberg antiferromagnet with the Dzyaloshinskii-Moriya (DM) interaction. Using the spin-wave theory quantum correction to the energy, on-site magnetization, and uniform magnetization are calculated as a function of the field H and the DM anisotropy constant D. It is shown that the spin-wave excitations exhibit an unusual field-evolution of the gaps. This leads to various non-analytic dependencies of the quantum corrections on H and D. It is also demonstrated that, quite generally, the DM interaction suppresses quantum fluctuations, thus driving the system to a more classical ground state. Most of the discussion is devoted to the spin-S, two-dimensional square lattice antiferromagnet, whose S=1/2 case is closely realized in K2V3O8 where at H=0 the DM anisotropy is hidden by the easy-axis anisotropy but is revealed in a finite field. The theoretical results for the field-dependence of the spin-excitation gaps in this material are presented and the implications for other systems are discussed.