Bloch oscillations, Zener tunneling and Wannier-Stark ladders in the time-domain

We present a time-domain analysis of carrier dynamics in a semiconductor superlattice with two minibands. Integration of the density-matrix equations of motion reveals a number of new features: (i) for certain values of the applied static electric field strong interband transitions occur; (ii) in static fields the complex time-dependence of the density-matrix displays a sequence of stable plateaus in the low field regime, and (iii) for applied fields with a periodic time-dependence the dynamic response can be understood in terms of the quasienergy spectra.Comment: 4 pages, 6 PostScript figures available from [email protected], REVTEX 3.

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.Comment: 15 pages, Revtex 3.0, uses epsf, 2 ps figures attache