Figure 5: Thermal Hall effect.

(a) Thermal Hall conductivity versus external magnetic field at different temperatures. The threshold fields h^z=±h_c are shown as vertical dashed lines. (b) Thermal Hall signal at h^z=h_c/2 versus temperature. The circles are direct evaluation of the formula, the line is an approximation applicable to SrCu₂(BO₃)₂ in the limit where bandwidths are much smaller than the gap. (c) The filling fraction (boson occupation number) for the three bands, indexed by Chern numbers. It grows much slower with temperature than κ^xy.