‘Mobility gap’ of a spin-split GaAs two-dimensional electron gas

Abstract

We have performed magnetotransport measurements of the electron g-factor in a two-dimensional GaAs electron gas. In order to obtain the spin gap Δ s, we measure the spin-split longitudinal resistivity minimum which shows an activated behavior. From the spin gaps at different odd filling factors, we can obtain the effective g-factor which is greatly enhanced over its bare value (0.44) in GaAs. This enhancement is due to many-body electron–electron interactions. Our experimental results provide compelling evidence that conventional activation energy studies yield a ‘mobility gap’ which can be very different from the real spin gap in the energy spectrum.