Extended Data Fig. 7: Predicted QO spectra and possible mechanism of interband scattering.

The dependence of the QO frequencies on energy is key to understanding their temperature dependence. a, FFT amplitude of equation (11) over an extended B-field range at T = 0. As well as equation (11), leading contributions up to the fourth order in the Dingle factor are included, which can be evaluated systematically. Experimental values for \({m}_{\lambda }^{* }\) and T_D,λ ≈ 0.5 K were used consistent with CoSi, as well as f_α(E), f_β(E) from the DFT calculations. b, Cut along E = E_F for CoSi. This may be compared with the spectrum recorded experimentally. Peaks shown in panels a and b seem broad because of the log scale. c, Band structure of the effective k ⋅ p Hamiltonian around the R point equation (12) used to model a possible mechanism for nonlinear interband scattering. d, Schematic FSs in the effective k ⋅ p Hamiltonian (projection on the k_z = 0 plane with respect to R) in which the spin is polarized perpendicular to the FS and orientated in opposing directions on the two bands. This is consistent with results obtained in DFT calculations³⁶.