Coherent control of Bloch oscillations-from breathing mode quantum beats to spatial oscillations

Summary form only given. We present new results that show directly that the spatial motion of the wavepacket can be controlled by the laser excitation. For excitation below and above the center of the Wannier-Stark ladder (WSL), the wave packet performs a pronounced harmonic oscillation. In between, temporal oscillations, which are only associated with small center-of-mass amplitudes (so-called breathing modes), are observed. We shows total peak shifts of the WSL transition in a 67/17 /spl Aring/ GaAs-AlGaAs semiconductor superlattice (SL) as a function of the center energy of the excitation laser pulse.