Spin-dependent transport in a two-dimensional GaAs electron system

We have measured the low-temperature electron transport properties in a fro nt-gated GaAs/Al0.33Ga0.67As heterostructure. Collapse of spin-splitting an d an enhanced Lande \g\-factor at both Landau level filling factors nu = 3 and nu = 1 were observed. Our experimental results show direct evidence tha t the electron-electron interactions are stronger at v = 3 than those at v = 1 over approximately the same perpendicular magnetic field range. Moreove r, we observed an enhancement of the magnetoresistivity of a two-dimensiona l electron system with an increasing parallel magnetic field. Using a simpl e model, we suggest that the increase of the magnetoresistivity is due to s pin but the model over-estimates the Lande \g\ factor in our system.