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

Half-integer thermal quantum Hall conductance has recently been reported for the two-dimensional honeycomb material a-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 a-RuCl3.