Intersubband electron transitions due to electron-electron interactions in quantum-well structures

We have developed a full random-phase approximation formalism, and an efficient computational scheme for calculating the electron-electron scattering rates in quantum wells in nonequilibrium steady state, including the full dynamic screening. We apply our formalism to quantum-well systems studied in two recent experiments, which report different scattering rates for similar structures and similar carrier densities, and obtain quantitative agreement with both experiments. We show that the observed difference in the scattering rates is the result of different excitation levels in these experiments. We have also shown that the temperature dependence of the intersubband electron-electron scattering rate in one of the experiments is dominated by the higher-order, noncollective electron-electron scattering events at low temperature. We propose a scenario that could lead to the dominance of the electron-plasmon (collective) scattering processes. One of the experimental indications of this would be an activated temperature dependency of the intersubband electron-electron scattering rate.