Half-integer quantized anomalous thermal Hall effect in the Kitaev material candidate α-RuCl3

A thermal signature Although the material α-ruthenium chloride exhibits some of the physics associated with Kitaev spin liquids, it is not a perfect representation of this model. Yokoi et al. probed the limits of the Kitaev description by studying the thermal Hall response in this material. Applying an external magnetic field both in the plane of the sample and at an angle to it, the researchers observed a half-integer quantization of the thermal Hall signal. The findings suggest the formation of a topological state consistent with the Kitaev model. Science, aay5551, this issue p. 568 Thermal Hall response is consistent with the formation of an unusual topological order. Half-integer thermal quantum Hall conductance has recently been reported for the two-dimensional honeycomb material α-RuCl3. We found that the half-integer thermal Hall plateau appears even for a magnetic field with no out-of-plane components. The measured field-angular variation of the quantized thermal Hall conductance has the same sign structure as the topological Chern number of the pure Kitaev spin liquid. This observation suggests that the non-Abelian topological order associated with fractionalization of the local magnetic moments persists even in the presence of non-Kitaev interactions in α-RuCl3.