A distinct thermal Hall signal is observed in a quantum spin liquid candidate Ba3CuSb2O9. The transverse thermal conduction shows a power-law temperature dependence below 40 K where a spin gap opens. We suggest that, through the very low longitudinal thermal conductivity and the thermal Hall signals, a phonon Hall effect is induced by strong phonon scatterings by orphan Cu2+ spins formed in random domains of Cu2+-Sb5+ dumbbells.
@article{arxiv.1608.07401,
title = {Thermal Hall effect in a phonon-glass Ba$_3$CuSb$_2$O$_9$},
author = {Kaori Sugii and Masaaki Shimozawa and Daiki Watanabe and Yoshitaka Suzuki and Mario Halim and Motoi Kimata and Yosuke Matsumoto and Satoru Nakatsuji and Minoru Yamashita},
journal= {arXiv preprint arXiv:1608.07401},
year = {2017}
}