Depolarization shift of the intersubband resonance in a quantum well with an electron-hole plasma

We study the depolarization shift of the electronic intersubband resonance at various electron-hole plasma densities. Using a time-resolved interband-pump–intersubband-probe technique, we measure the intersubband transitions in GaAs quantum wells. The pump pulse generates an electron-hole plasma, which then gradually decays by radiative recombination, while the probe pulse monitors the conduction band intersubband absorption spectrum as a function of the momentary plasma density. The measured time/density-dependent shift of the intersubband resonance energy is quantitatively explained by a density functional model accounting for the static and dynamic many-body effects in the electron-hole plasma. It turns out that the holes play an important role in minimizing the static Hartree potential. Their presence, however, does not significantly affect the measured dynamic depolarization shift of the electronic intersubband resonance.