New Features in the Field-dependent Thermal Conductivity of α-RuCl3 at Low Temperatures*

α-RuCl3 is currently the most promising and well-studied candidate for realizing the unique physics of the Kitaev model. Because the energy scale of the exchange interactions is understood to be quite high (J ~ 100K), measurements at low temperatures have been somewhat scarce and it’s behavior below 2K remains largely unexplored. This is especially true for thermal transport experiments, which have proven to be an incredibly powerful probe of excitations and phase transitions in insulating magnets. We present measurements of the thermal conductivity as a function of temperature and in-plane magnetic field that were performed between 0.4 and 1.7K. We identify several new features in κ_xx(B) that occur between 7 and 11T, a regime located between the long range ordered and fully polarized states and where spin liquid behavior is thought to occur. Possible explanations for these new features as well as their relation to the recent observation of a half-integer quantized thermal hall conductance will be discussed.