Magnon-induced scalar spin chirality in Kagome and honeycomb ferromagnets

TL;DR

This paper reveals that thermally excited magnons can induce scalar spin chirality in collinear ferromagnets on Kagome and honeycomb lattices, highlighting a new mechanism for chiral phenomena at finite temperatures.

Contribution

It demonstrates that magnons can generate scalar spin chirality in collinear spin systems via Dzyaloshinskii-Moriya interactions, a novel insight into chiral physics in magnetic materials.

Findings

Magnon-induced SSC increases with DMI and temperature.

Finite SSC can reach magnitudes comparable to non-coplanar configurations.

SSC emerges at finite temperature in collinear ferromagnets due to thermal magnons.

Abstract

The scalar spin chirality (SSC), defined as a triple product of spins, is essential for describing noncoplanar spin structures and understanding chiral physics in magnetic systems. Traditionally, SSC has been discussed primarily in the context of noncoplanar ground-state spin configurations at zero temperature, as collinear spin systems are generally thought to lack SSC. Consequently, whether the SSC can emerge at finite temperatures in spin systems with collinear ground states remains an open question and has yet to be fully understood. In this study, we theoretically demonstrate that thermally excited magnons can induce SSC even in collinear spin systems. By considering 2D ferromagnets on Kagome and honeycomb lattices, we demonstrate that the Dzyaloshinskii-Moriya interactions (DMI) which break the effective time-reversal symmetry in the magnon Hamiltonian can lead to finite SSC at finite temperatures. Using a simple spin model, we show both numerically and analytically that the SSC increases with the magnitude of DMI and temperature. Furthermore, calculations based on realistic material parameters reveal that the magnon-induced SSC can achieve a magnitude comparable to those observed in non-coplanar spin configurations. These findings suggest that SSC plays a significant role even in collinear spin systems, providing new insights into the chiral physics of magnetic materials.