Enhancement of the spin gap in fully occupied two-dimensional Landau levels

Abstract

Polarization-resolved magnetoluminescence, together with simultaneous magnetotransport measurements, have been performed on a two-dimensional electron gas (2DEG) confined in CdTe quantum well in order to determine the spin splitting of fully occupied electronic Landau levels, as a function of the magnetic field (arbitrary Landau-level filling factors) and temperature. The spin splitting, extracted from the energy separation of the ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}}$ transitions, is composed of the ordinary Zeeman term and a many-body contribution which is shown to be driven by the spin polarization of the 2DEG. It is argued that both these contributions result in a simple, rigid shift of Landau-level ladders with opposite spins.