Chiral fluctuations in triangular antiferromagnets at $T \ll T_N$

TL;DR

This paper theoretically investigates chiral fluctuations in triangular antiferromagnets at temperatures much lower than the Néel temperature, revealing nonzero dynamical chirality even without external Dzyaloshinskii-Moriya interaction or magnetic field.

Contribution

It provides analytical expressions for dynamical chirality in TAFs using linear spin-wave theory, highlighting unique nonzero chirality in one-domain samples without external interactions.

Findings

Dynamical chirality is nonzero at zero D and H in TAFs.

Ground state axial vector causes nonzero chirality.

Results apply to quantum TAF CsCuCl$_3$.

Abstract

Chiral fluctuations in triangular antiferromagnets (TAFs) at $T \ll T_N$ are studied theoretically. The case of a ferromagnetic interaction along c axis (which is directed perpendicular to the plane of the lattice), Dzyaloshinskii-Moriya interaction ${\bf D}\| c$ and a weak magnetic field ${\bf H}\| c$ is considered in detail. Previously, this model has been proposed to describe quantum TAF CsCuCl$_3$. Expressions for dynamical chirality (DC) are derived within the linear spin-wave approximation. In contrast to non-frustrated antiferromagnets, DC is found to be nonzero even at $D,H=0$ in a one-domain sample. We argue that this unusual behavior stems from the fact that a ground state of XY and Heisenberg TAFs is characterized by an axial vector along which DC is directed.