INTERACTIONS BETWEEN WANNIER-STARK STATES

We examine the interaction between the Wannier-Stark ladders derived f rom two minibands in a semiconductor superlattice. We show that it lea ds to anticrossings whose magnitude and electric field position can be modelled in a simple way. The eigenenergies depart from a linear depe ndence upon the electric field. In the time domain, the wavepackets sh ow 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 cont rast to the one band case, a net absorption or emission becomes possib le, although not at the Bloch frequency.