Bloch oscillations under influence of coherent plasmon coupling

Summary form only given. Bloch oscillations (BO) of electrons in a periodic system under applied electric field are a very basic transport effect and have been investigated in several experiments in semiconductor superlattices. In time resolved optical experiments, BO were studied by the excitation of wave packets of Wannier-Stark ladder (WSL) states and detection of four-wave mixing signals, THz radiation, and the direct measurement of harmonic spatial oscillations caused by the induced dipole field. We investigate the interaction of Bloch oscillations with the background plasma oscillations. For higher carrier densities, the motion of the wave packet becomes strongly anharmonic and subsequently the BO break down. This determines a limit for the operation of emitter devices which are based on high carrier densities. The experiments are performed on a GaAs/AlGaAs superlattice with a miniband of about 40 meV. We use transient four-wave mixing experiments (FWM) to trace the amplitude of the wave packet motion. This method relies on the induced electric dipole field which modulates the WSL transitions with delay time. The peak shift of the WSL transitions caused by this dipole can be deduced from the spectrally resolved FWM signal.