SPIN-SPLITTING AND LANDAU-SPLITTING OF THE CYCLOTRON-RESONANCE IN A NONPARABOLIC 2-DIMENSIONAL ELECTRON-SYSTEM

We study cyclotron resonance (CR) in a two-dimensional electron system on InAs/AlSb-quantum wells observing discrete transitions between adj acent sets of spin-split Landau states. While in three-dimensional ele ctron systems such splittings are Well established, no spin-split CR h as been observed in a two-dimensional electron system, to date. Theore tical attempts link this fact to the reduced dimensionality and strong electron-electron coupling. Our results, however, can be interpreted quantitatively in a straightforward single-particle model offering new clues to this major puzzle.