The Kitaev quantum spin liquid displays the fractionalization of quantum spins into Majorana fermions. The emergent Majorana edge current is predicted to manifest itself in the form of a finite thermal Hall effect, a feature commonly discussed in topological superconductors. Here we report on thermal Hall conductivity κxy measurements in α-RuCl3, a candidate Kitaev magnet with the two-dimensional honeycomb lattice. In a spin-liquid (Kitaev paramagnetic) state below the temperature characterized by the Kitaev interaction JK/kB∼80 K, positive κxy develops gradually upon cooling, demonstrating the presence of highly unusual itinerant excitations. Although the zero-temperature property is masked by the magnetic ordering at TN=7 K, the sign, magnitude, and T-dependence of κxy/T at intermediate temperatures follows the predicted trend of the itinerant Majorana excitations.
@article{arxiv.1709.10286,
title = {Unusual thermal Hall effect in a Kitaev spin liquid candidate $\alpha$-RuCl$_3$},
author = {Y. Kasahara and K. Sugii and T. Ohnishi and M. Shimozawa and M. Yamashita and N. Kurita and H. Tanaka and J. Nasu and Y. Motome and T. Shibauchi and Y. Matsuda},
journal= {arXiv preprint arXiv:1709.10286},
year = {2018}
}