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Direct measurement of the spatial displacement of bloch-oscillating electrons in semiconductor superlattices
Direkte Messung der räumlichen Verschiebung von Bloch-Oszillierenden Elektronen in Halbleiter-Übergittern
Bloch oscillations in semiconductor superlattices have recently been observed using optical techniques. However, it remained to show that the optically observed quantum beats of the Wannier-Stark ladder are connected with a true spatial oscillation of the wave packet. We present an experimental technique which measures directly the displacment of the wave packet center-of-mass: The oscillating Bloch wave packets create a microscopic dipole moment which can he determined using the shift of the Wannier-Stark ladder transition energy as a sensitive dipole field detector. We show that the wave packet undergoes harmonic spatial motion in accordance with the predictions of Bloch and Zener.