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

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.

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