Torque anomalies at magnetization plateaux in quantum magnets with Dzyaloshinskii-Moriya interactions

TL;DR

This paper studies how Dzyaloshinskii-Moriya interactions influence torque measurements in quantum magnets with magnetization plateaux, revealing peaks at critical fields and proposing experimental detection methods.

Contribution

It demonstrates that DM interactions cause distinctive torque anomalies at critical fields and suggests a sensitive experimental approach for their detection.

Findings

Torque peaks at critical fields due to DM interactions

Non-monotonous torque behavior with large DM interactions

Sensitive detection of critical fields near principal g-tensor directions

Abstract

We investigate the effect of Dzyaloshinskii-Moriya (DM) interactions on torque measurements of quantum magnets with magnetization plateaux in the context of a frustrated spin-1/2 ladder. Using extensive DMRG simulations, we show that the DM contribution to the torque is peaked at the critical fields, and that the total torque is non-monotonous if the DM interaction is large enough compared to the g-tensor anisotropy. More remarkably, if the DM vectors point in a principal direction of the g-tensor, torque measurements close to this direction will show well defined peaks even for small DM interaction, leading to a very sensitive way to detect the critical fields. We propose to test this effect in the two-dimensional plateau system SrCu$_2$(BO$_3$)$_2$.