Quantum Aspects of the Azbel'-Kaner Resonance in Bismuth

We report the observation of Azbel'-Kaner cyclotron resonance in the limit where distinct transitions between quantized levels have to be considered. A multiplet structure is found in the subharmonic resonances arising from the unequal spacing of the Landau levels in the nonparabolic conduction band of Bi. The data are satisfactorily interpreted in terms of the ellipsoidal-nonparabolic band-structure model due to Lax. The sharpness of the resonances $\frac{\Delta H}{H}\lesssim 2\%$ makes it possible to re-examine previously reported band-structure parameters of this model.