Electron transport in superlattices for interacting Wannier-Stark levels

We develop a microscopic theory of electron transport in superlattices within the Wannier-Stark approach by including the interaction among the energy levels pertaining to adjacent quantum wells. The main results are: (i) the interaction among the levels is responsible for a systematic increase of the level energy with respect to the bottom of the quantum well at increasing electric fields; (ii) the interaction is responsible for the onset of a new delocalization of the Wannier-Stark states at the highest fields associated with the tunneling of electrons between adjacent quantum wells; (iii) with respect to the non-interacting case, at the highest fields the average carrier energy evidences a consistent increase which leads to a significant softening of the negative differential value of both the drift velocity and diffusivity. [GRAPHICS] The potential profile and the squared wavefunction corresponding to a Wannier-Stark level which includes the coupling with the field for an electric field of 200 kV/cm. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.