Phonon thermal Hall effect from scattering off two-level systems

With the growing number of experiments observing the phonon thermal Hall effect, it becomes crucial to investigate the underlying theoretical aspects and the correlations probed by this phenomenon. In my talk, I will delve into the exploration of an extrinsic scattering mechanism of phonons called the side-jump mechanism. By focusing on this mechanism, I aim to address the question of how the phonon thermal Hall effect relates to two-point correlations in materials. I will demonstrate that even a simple two-level system, when coupled to phonons, can induce a thermal Hall effect, thereby explaining recent experiments in quantum spin ice Pr2Ir2O7 and cuprates.