Nonequilibrium many body theory for quantum transport in terahertz quantum cascade lasers

This paper presents a predictive Keldysh nonequilibrium many body Green’s functions theory for quantum transport including high order electron-electron, electron-phonon, electron-impurity, and interface roughness scattering processes. Our approach is fully frequency and momentum dependent including nondiagonal dephasing terms in both frequency and k-space. A detailed balance between coherent and scattering processes leads to local current conservation even if a small number of states is considered. Good agreement with experiments is obtained for a terahertz quantum cascade laser.