Theory of Cyclotron Resonance Line Width

Abstract

Absorption of microwave near the cyclotron resonance by free carriers in a strong magnetic field is treated quantum-mechanically on the assumption of elastic scattering by impurities and phonons. It is pointed out that the homogeneous broadening is determined by a relaxation time τ c which is analogous to the transport relaxation time for d c conductivity and is generally equal neither to the life time of Landau levels nor to any kind of its mean value. The behavior of τ c in the quantum limit is discussed for various mechanisms of scattering. For scattering by piezoelectric phonons at finite temperatures τ c becomes finite although the life time of a Landau level vanishes in the second order perturbation.