Thermal Hall conductivity in the cuprate Mott insulators Nd2CuO4 and Sr2CuO2Cl2

Abstract

What makes the phonons in cuprates become chiral, as measured by their thermal Hall effect, is an unresolved question. Here, the authors rule out two extrinsic mechanisms and argue that chirality comes from a coupling of acoustic phonons to the intrinsic excitations of the CuO2 planes.