Thermal Hall conductivity in the cuprate Mott insulators NdCuO and SrCuOCl.

The heat carriers responsible for the unexpectedly large thermal Hall conductivity of the cuprate Mott insulator LaCuO were recently shown to be phonons. However, the mechanism by which phonons in cuprates acquire chirality in a magnetic field is still unknown. Here, we report a similar thermal Hall conductivity in two cuprate Mott insulators with significantly different crystal structures and magnetic orders - NdCuO and SrCuOCl - and show that two potential mechanisms can be excluded - the scattering of phonons by rare-earth impurities and by structural domains.