Fig. 3

Simulations of the spectrum dispersion in YIG. a The previous model^3,28 and b our new model of the magnon dispersion, where the colour and intensity correspond to the sign and magnitude of the spectral function S_xy(Q,ω) − S_yx(Q,ω) averaged over many Brillouin zones, which is responsible for the spin Seebeck effect.²⁸ Results are plotted for the centred (i.e. non-primitive) cell. Red and blue modes have positive and negative values of the spectral function and are associated with spin currents that flow in opposite directions. The horizontal dashed line indicates k_BT at room temperature