INTERACTIONS BETWEEN WANNIER-STARK STATES

We examine the interaction between the Wannier-Stark ladders derived from two minibands in a semiconductor superlattice. We show that it leads to anticrossings whose magnitude and electric field position can be modelled in a simple way. The eigenenergies depart from a linear dependence upon the electric field. In the time domain, the wavepackets show spatial oscillations between the main locations of the particle in the two interacting states. The frequency of the absorbed and emitted photons between such unevenly spaced ladders become different. In contrast to the one band case, a net absorption or emission becomes possible, although not at the Bloch frequency.