Charged defects and phonon Hall effects in ionic crystals

It has been known for decades that a magnetic field can deflect phonons as they flow in response to thermal gradient, producing Hall effect. Several recent experiments have revealed ratios of the phonon conductivity longitudinal oxide dielectrics are larger than $10^{-3}$ when mean-free-paths exceed wavelengths. At same time $\kappa_{H}/\kappa_{L}$ is not strongly temperature dependent. We argue these two properties together imply mechanism related scattering from defects break time-reversal symmetry, and we show Lorentz forces acting on charged produce substantial skew-scattering amplitudes, effects consistent with observations.