Figure 1.

Thermal Hall effect of charge-neutral excitations

(A) Schematic illustration of the thermal Hall effect.

(B) Measured ${\kappa }_{xy}$ as a function of ${\kappa }_{xx}$ for several quantum materials, in which solid and open symbols represent ${\kappa }_{xy}$ due to phonons1, 2, 3 and spins,4, 5, 6, 7 respectively.