Coherent response of a biased double-well superlattice subjected to an ultrashort interband excitation

The temporal evolution of electrons in a biased double-well superlattice, subjected to an ultrashort interband excitation, is theoretically examined. Both the temporal oscillations of the induced current and the evolution of the photoexcited electron concentration are considered for different parameters of the structure subjected to a δ-pulse excitation. Due to the mixing of the Wannier–Stark-ladder branches, the induced response depends on the applied bias voltage in a complicated way. In particular, long-time beats appear in the vicinities of intra- and inter-cell anti-crossings of the energy spectrum. These dependencies are examined within the framework of the Kane model, invoking the parabolic approximation for electron and heavy hole states. Numerical calculations of the carrier coherent dynamics are performed for the case of a δ-pulse excitation and with a phenomenologically introduced damping factor.