Phonon thermal Hall effect in charge-compensated topological insulators

The observation of surprisingly large thermal Hall ratios in a growing number of mainly oxide-based insulators is a major puzzle and raises the question about potential mechanisms that can induce a thermal Hall effect in materials with dominant charge-neutral heat carriers. Here, the authors report the finding of comparable thermal Hall ratios in a series of charge-compensated topological insulators and discuss this observation in the context of a recent proposal that a thermal Hall effect can result from skew scattering of phonons on charged defects.