Dynamic localization leading to full suppression of the dc current in a GaAs/AlAs superlattice

We demonstrate that a strong THz-field (3.9 THz) can lead to full supression of the de current through a GaAs/AlAs superlattice that shows, at room temperature, negative differential conductance. The miniband width (Delta = 50 meV) was much larger than the quantum energy of the radiation (16 meV). Using a semi-classical model we show that the miniband electrons do not relax during one period of the THz-field. In this case the reduction of the de current can not be explained in terms of classical rectification caused by the non-linear current-voltage characteristic. Rather it is due to dynamic localization of electrons, performing frequency modulated Bloch oscillations. (C) 1997 Academic Press Limited