Magnetic oscillations of resistivity and absorption of radiation in quantum wells with two populated subbands

The dynamic (ac) conductivity tensor of quantum wells with two populated subbands in the presence of a magnetic field perpendicular to the well layer is calculated theoretically. The microscopic theory is based on the Kubo formalism assuming a detailed consideration of elastic scattering of electrons by the random disorder potential with arbitrary correlation length. The results describe the influence of magnetic field on the linear absorption of low-frequency electromagnetic radiation, and demonstrate the existence of magnetic oscillations that survive at high temperatures and whose maxima correspond to absorption of electromagnetic radiation at combined frequencies, determined by both the magnetic field and the subband separation. Different polarizations of the radiation field with respect to the quantum-well layer are considered. Analytical expressions are derived for the case of sufficiently weak magnetic field when the Landau levels are overlapping. Application of the theory to the static (dc) limit provides a consistent description of the magneto-intersubband oscillations of the resistivity in the systems with two populated subbands.