Self-consistent random-phase approximation for interacting electrons in quantum wells and intersubband absorption

For electrons with Coulomb interaction confined in a quantum well, we have developed an approach based on the Kadanoff-Baym-Keldysh technique to calculate equilibrium Green’s functions. This approach is based on iterative numerical computation of the retarded self-energy in the self-consistent random-phase approximation. For two subbands, at zero temperature, we have computed spectral functions, electron distributions, quasiparticle spectra, and the current-current correlation function that determines the intersubband absorption coefficient. Our computations of the optical absorption take into account the depolarization shift and vertex corrections. Apart from direct applications of this theory to the physics of semiconductor quantum well devices, the Green’s functions obtained may also serve as self-consistent initial conditions for quantum kinetics problems in quantum wells.