On the theory of electromagnetic waves in anisotropic metals

Abstract

Doppler-shifted cyclotron resonance is studied for a simple model Fermi surface which includes a small pocket of paraboloidal form. This model is simple enough for the field dependence of all the wave characteristics to be found analytically. The results depend on the relative distances moved by the different groups of charge carriers, in the direction of the applied magnetic field, during one cyclotron period. When this displacement is larger for the carriers on the paraboloid than for the main carriers, the helicon wave is coupled with the DSCR mode. It is found that the properties of the coupled waves depend significantly on the sign of the resonant term in the conductivity with respect to the Hall conductivity due to the main carriers. If the signs coincide, the coupling results in extrema in the wave spectrum and anomalies in the impedance of the metal. If the signs are different the helicon wave transforms smoothly into the DSCR mode at the resonance. When the displacement of the carriers on the paraboloid is smaller than for the majority of carriers a DSCR propagating mode appears below the helicon absorption edge.