Spin Thermal Hall Conductivity of a Kagom\'e Antiferromagnet

A clear thermal Hall signal (${\kappa }_{xy}$) was observed in the spin liquid phase of the $S=1\mathrm{/}2$ kagom'e antiferromagnet Ca kapellasite (CaCu${}_3$(OH)${}_6$Cl${}_2\cdot 0.6$H${}_2$O). We found that ${\kappa }_{xy}$ is well reproduced, both qualitatively and quantitatively, using the Schwinger-boson mean-field theory with the Dzyaloshinskii–Moriya interaction of $D/J \sim 0.1$\mathrm{.}Inparticular,$\kappa_{xy}$ values of Ca kapellasite and those of another kagom'e antiferromagnet, volborthite, converge to one single curve in simulations modeled using Schwinger bosons, indicating a common temperature dependence of ${\kappa }_{xy}$ for the spins of a kagom'e antiferromagnet.