Halperin-Saslow modes as the origin of the low temperature anomaly in $NiGa_2S_4$

TL;DR

This paper explains the low temperature anomalies in NiGa₂S₄ through Halperin-Saslow modes, suggesting a novel quantum ground state with linearly dispersing excitations in a system lacking magnetic long-range order.

Contribution

It demonstrates that Halperin-Saslow modes can account for experimental observations in NiGa₂S₄, providing a new theoretical framework for understanding its quantum ground state.

Findings

Existence of linearly dispersing modes in NiGa₂S₄

Consistency of Halperin-Saslow modes with experimental data

Constraints on microscopic theories of NiGa₂S₄

Abstract

The absence of magnetic long range order in the triangular lattice spin-1 antiferromagnet $NiGa$_2$S$_4$ has prompted the search for a novel quantum ground state. In particular, several experiments suggest the presence of a linearly dispersing mode despite no long-range magnetic order. We show that the anomalous low temperature properties of NiGa$_2$S$_4$ can naturally be explained by the formulation developed by Halperin and Saslow where the linearly dispersing Halperin-Saslow mode may exist in the background of frozen spin moments and zero net magnetization. We provide highly non-trivial consistency checks on the existing experimental data and suggest future experiments that can further confirm the existence of the Halperin-Saslow mode. Our results place strong constraints on any microscopic theory of this material.