Thermal Properties and Instability of a $U(1)$ Spin Liquid on the Triangular Lattice

TL;DR

This paper investigates how Dzyaloshinskii-Moriya interactions influence the thermal and magnetic properties of a $U(1)$ quantum spin liquid on a triangular lattice, revealing effects on stability, thermal conductance, and phase transitions.

Contribution

It introduces the impact of DM interactions on the $U(1)$ QSL, including flux induction, Berry phase effects, and phase transitions to spin density wave and antiferromagnetic states.

Findings

Weak DM induces staggered flux and modifies spinon density of states.

In-plane DM components lead to nonzero Berry phases affecting thermal conductance.

Larger DM interactions trigger a spin density wave due to Fermi surface nesting.

Abstract

We study the effect of Dzyaloshinskii-Moriya (DM) interaction on the triangular lattice $U(1)$ quantum spin liquid (QSL) which is stabilized by ring-exchange interactions. A weak DM interaction introduces a staggered flux to the $U(1)$ QSL state and changes the density of states at the spinon fermi surface. If the DM vector contains in-plane components, then the spinons gain nonzero Berry phase. The resultant thermal conductances $\kappa_{xx}$ and $\kappa_{xy}$ qualitatively agree with the experimental results on the material EtMe$_3$Sb[Pd(dmit)$_2]_2$. Furthermore, owing to perfect nesting of the fermi surface, a spin density wave state is triggered by larger DM interactions. On the other hand, when the ring-exchange interaction decreases, another anti-ferromagnetic (AFM) phase with $120^\circ$ order shows up which is proximate to a $U(1)$ Dirac QSL. We discuss the difference of the two AFM phases from their static structure factors and excitation spectra.