Anticrossings of spin-split Landau levels in an InAs two-dimensional electron gas with spin-orbit coupling

We report tilted-field transport measurements in the quantum Hall regime in an InAs/In0.75Ga0.25As/In0.75Al0.25As quantum well. We observe anticrossings of spin-split Landau levels, which suggest a mixing of spin states at Landau level coincidence. We propose that the level repulsion is due to the presence of spin-orbit and of band-nonparabolicity terms which are relevant in narrow-gap systems. Furthermore, electron-electron interaction is significant in our structure, as demonstrated by the large values of the interaction-induced enhancement of the electronic g factor.