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Fresh insights into electron oscillations

In 1934, during the early days of quantum mechanics, Carl Zener used the ideas of Felix Bloch to predict that the electrons in a crystalline solid would oscillate at high frequencies when subjected to a constant electric field. However, these so-called Bloch oscillations were not detected until five years ago, when their observation was made possible by the availability of semiconductor superlattices and ultrashort laser pulses. Now, for the first time, Karl Leo and colleagues at the Technical University of Dresden in Germany have used a novel optical technique to precisely determine the high-frequency electric field generated in the superlattice by the oscillating electrons. From the data, they were able to derive the spatial dynamics of the electrons (V G Lyssenko et al. 1997 Phys. Rev. Lett. 79 301).