Delayed intersubband relaxation in quantum wires due to quantum kinetic Coulomb scattering

A theoretical analysis of the ultrafast intrasubband and intersubband dynamics of optically excited electrons in quantum wires is presented within the density matrix formalism. It is shown that the inclusion of non-Markovian electron-electron quantum kinetics, in addition to semiclassical optical phonon scattering, is necessary for an appropriate description. In particular, the dynamics of the two-particle density correlations must be explicitly taken into account. The electron-electron scattering processes, which are strongly restricted in quantum wires by energy and momentum conservation, are substantially enhanced on the quantum kinetic level, leading to fast intrasubband thermalization, and intersubband redistribution of the electrons which substantially delays the phonon-induced intersubband relaxation. Our simulations predict that the influence of electron-electron scattering becomes noticeable already at electron densities per unit length of the order of ${10}^6\hspace{0.5em}{\mathrm{}\mathrm{m}}^{-1}.$