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Magnetoconductivity oscillations induced by intersubband excitation in a degenerate 2D electron gas

Magnetoconductivity oscillations and absolute negative conductivity induced by nonequilibrium populations of excited subbands in a degenerate multisubband two-dimensional electron system are studied theoretically. The displacement from equilibrium, which can be caused by resonant microwave excitation or by any other reason, is assumed to be such that electron distributions can no longer be described by a single Fermi level. In this case, in addition to the well-known conductivity peaks occurring at the Shubnikov-de Haas conditions and small peaks of normal intersubband scattering, sign-changing oscillations with a different shape are shown to be possible. We found also that even a small fraction of electrons transferred to the excited subband can lead to negative conductivity effects.