Microwave-induced intersubband scattering and magneto-oscillation phenomena in an inhomogeneous 2D electron gas on liquid helium

Abstract

The theoretical description of microwave-induced intersubband scattering in a 2D electron gas exposed to a magnetic field on liquid helium with the inhomogeneous distribution of subband excitation energies is presented. We demonstrate that the alignment of the staircases of Landau levels in the ground and the first excited subbands differently affects the microwave resonant absorption and in-plane magnetoconductivity. In contrast with previously used models, the microwave excitation rate is shown to have a strong dependence on the magnetic field with sharp minima at the Landau level alignment points even in a heavily inhomogeneous 2D electron system. The inhomogeneous distribution of transverse-quantization eigenfrequencies changes the lineshape of the intersubband resonance and substantially broadens conductivity magneto-oscillations. These results explain unexpected experimental observations reported previously.