The population inversion and novel magnetoconductivity oscillations induced by resonant microwave irradiation in multi-subband two-dimensional electron systems

The possibility of a population inversion in a multi-subband two-dimensional (2D) electron system exposed to resonant microwave (MW) radiation and a static magnetic field is shown. Theoretical analysis given here indicates that the resonant excitation of the third subband, necessary for the population inversion, is accompanied by novel magnetoconductivity oscillations in the 2D electron system formed on the surface of liquid helium.