Exchange-enhanced Landé g-factor, effective disorder and collapse of spin-splitting in a two-dimensional GaAs electron system

We have measured the low-temperature transport properties of front-gated GaAs/Al0.33Ga0.67As heterostructures. Collapse of spin-splitting and an enhanced Landé |g|-factor at Landau level filling factors both ν=3 and 1 are observed. Our experimental results show direct evidence that the electron–electron interactions are stronger at ν=3 than those at ν=1 over approximately the same perpendicular magnetic field range.