Large Exchange Interactions in the Electron Gas of GaAs Quantum Wells.

Inelastic light scattering measurements show that exchange Coulomb interactions in the two-dimensional electron gas of GaAs microstructures are more important than previously anticipated. Small wavevector spectra from modulation-doped quantum wells exhibit unexpected single-particle intersubband transitions in addition to collective spin-density and charge-density modes. From the measured spectral energies the direct and exchange intersubband Coulomb interactions are determined and found to be of comparable strengths.