Field dependence of the quantum ground state in the Shastry-Sutherland system SrCu$_2$(BO$_3$)$_2$

TL;DR

This study investigates the magnetic properties of SrCu$_2$(BO$_3$)$_2$ under high magnetic fields, revealing a new quantum phase and highlighting the significant role of Dzyaloshinskii-Moriya interactions in its behavior.

Contribution

The paper reports the discovery of a new quantum phase in SrCu$_2$(BO$_3$)$_2$ above the 1/8 plateau using torque measurements, emphasizing the impact of Dzyaloshinskii-Moriya coupling.

Findings

Identification of a new quantum phase above the 1/8 plateau.

Large contribution of Dzyaloshinskii-Moriya interaction to torque response.

Observation of supercooling effects due to magnetocaloric phenomena.

Abstract

We present magnetic torque measurements on the Shastry-Sutherland quantum spin system SrCu$_2$(BO$_3$)$_2$ in fields up to 31 T and temperatures down to 50 mK. A new quantum phase is observed in a 1 T field range above the 1/8 plateau, in agreement with recent NMR results. Since the presence of the DM coupling precludes the existence of a true Bose-Einstein condensation and the formation of a supersolid phase in SrCu$_2$(BO$_3$)$_2$, the exact nature of the new phase in the vicinity of the plateau remains to be explained. Comparison between magnetization and torque data reveals a huge contribution of the Dzyaloshinskii-Moriya interaction to the torque response. Finally, our measurements demonstrate the existence of a supercooling due to adiabatic magnetocaloric effects in pulsed field experiments.