Spin Thermal Hall Conductivity of a Kagome Antiferromagnet

Abstract

A clear thermal Hall signal (${\ensuremath{\kappa}}_{xy}$) was observed in the spin-liquid phase of the $S=1/2$ kagome antiferromagnet Ca kapellasite $[{\mathrm{CaCu}}_{3}(\mathrm{OH}{)}_{6}{\mathrm{Cl}}_{2}\ifmmode\cdot\else\textperiodcentered\fi{}0.6{\mathrm{H}}_{2}\mathrm{O}]$. We found that ${\ensuremath{\kappa}}_{xy}$ is well reproduced, both qualitatively and quantitatively, using the Schwinger-boson mean-field theory with the Dzyaloshinskii-Moriya interaction of $D/J\ensuremath{\sim}0.1$. In particular, ${\ensuremath{\kappa}}_{xy}$ values of Ca kapellasite and those of another kagome antiferromagnet, volborthite, converge to one single curve in simulations modeled using Schwinger bosons, indicating a common temperature dependence of ${\ensuremath{\kappa}}_{xy}$ for the spins of a kagome antiferromagnet.