Rich field dependence of thermal transport in quantum spin ice candidate Yb₂Ti₂O₇

Thermal transport can be a very powerful tool for studying magnetic excitations in frustrated quantum systems. One such system whose excitations are of particular interest is Yb₂Ti₂O₇, a quantum spin ice candidate with a pseudospin-1/2 ground state that should give rise to strong quantum fluctuations. Here, we report field dependent (B ‖〈111〉) longitudinal and transverse thermal conductivity measurements made on a highly stoichiometric crystal of Yb₂Ti₂O₇ over a wide range of temperatures. Our results reveal a rich dependence of both κ_xx and κ_xy on temperature and magnetic field that provides new information about the system’s unconventional excitations. While some features are very reminiscent of previously reported measurements on Tb₂Ti₂O₇, another quantum spin ice candidate, others are quite novel. In particular, at very low temperatures, we observe a large positive thermal hall signal followed by a sign inversion at low fields, but features characteristic of conventional magnons at higher ones. These and other results as well as possible explanations will be discussed.