Acousto-helicon interaction in narrow-gap semiconductors

A theoretical investigation is made on the propagation of acousto-helicon waves through plasmas in narrow-gap semiconducting piezoelectric crystals. Interaction coupling of the acousto-helicon mode sets up at lower frequencies in the small-gap semiconductors as compared to that in wide-gap ones. This is because of the strong dependence of the electron effective mass on the nonparabolicity of the conduction band of the semiconductors. Results are also shown for wide-gap semiconductors for the sake of comparison.