Phonon Chirality and Thermal Hall Transport

In recent years, a rapidly increasing amount of studies has reported novel physical phenomena
arising from lattice vibrations that carry angular momentum, i.e., chiral phonons. In this talk, I will discuss both intrinsic and extrinsic sources of chiral acoustic phonon transport and their connection to phonon topology. First, I will show that in ionic crystals a phonon Hall viscosity contribution can emerge as a result of the Lorentz forces on moving ions. I will then explain how phonon scattering from defects that break time-reversal symmetry, such as charged impurities, can yield giant thermal Hall effects that are consistent with recent experimental observations.