Exchange enhancement of a spin-polarized 2D electron gas determined by optical-absorption spectroscopy

A large exchange enhancement of the spin-splitting of a two-dimensional electron gas in GaAs has been determined from optical spectroscopy. When the Fermi energy is located between the spin-split electron states ({ν}=1), we observe a striking temperature dependence in the optical absorption of interband transitions associated with both spin levels. The absorption intensity of the transitions monitors the occupations of the spin-split levels. Analysis of the temperature dependence reveals an exchange enhancement of the electron g factor of {}9. .AE