Theory of Coherent Time-dependent Transport in One-dimensional Multiband   Semiconductor Superlattices
  We present an analytical study of one-dimensional semiconductor superlattices in external electric fields, which may be time-dependent. A number of general results for the (quasi)energies and eigenstates are derived. An equation of motion for the density matrix is obtained for a two-band model, and the properties of the solutions are analyzed. An expression for the current is obtained. Finally, Zener-tunneling in a two-band tight-binding model is considered. The present work gives the background and an extension of the theoretical framework underlying our recent Letter [J. Rotvig {\it et al.}, Phys. Rev. Lett. {\bf 74}, 1831 (1995)], where a set of numerical simulations were presented. 
Jon Rotvig (1), Antti-Pekka Jauho (2), and Henrik Smith (1) ((1)   University of Copenhagen, (2) Technical Univ. of Denmark)