High Field ESR in the Two-Dimensional Triangular Lattice Antiferromagnet NiGa2S4

TL;DR

This study uses high-field ESR measurements on NiGa2S4 to explore spin dynamics, revealing Z2 vortex effects and a topological transition consistent with spin wave theory.

Contribution

First high-field ESR analysis of NiGa2S4 demonstrating the influence of Z2 vortices on spin dynamics and identifying a topological transition.

Findings

ESR linewidth influenced by Z2 vortex dynamics

Resonance fields match spin wave theory at 1.3 K

Evidence of Z2 vortex-induced topological transition

Abstract

In this Letter, we report the results of ESR measurements in high magnetic fields up to about 53 T on single crystals of NiGa2S4 to clarify the spin dynamics in more detail. We have found that the dynamics of Z2 vortices affects the temperature dependence of the ESR absorption linewidth and the frequency dependence of the ESR resonance fields at 1.3 K is well explained by a conventional spin wave theory. These results suggest an occurrence of Z2 vortex-induced topological transition.