Phonon-induced collapse of minibands in superlattices

The dynamic effect of electrons in a superlattice is studied in the presence of time-periodic barriers and quantum wells which simulate the electron-phonon interaction for an isolated inelastic-scattering process. The extended or localized nature of Floquet states is demonstrated to be controlled by the phonon frequency and the strength of the strain field. If the ratio of the renormalized average static potential and the phonon frequency is a root of the ordinary Bessel function of order zero, the quasienergy miniband will collapse. Correspondingly the extended motion of the electron turns into localization This phonon-induced localization stems from the interplay of the spatial periodicity of the superlattice and the temporal periodicity of the strain field. (C) 1997 Published by Elsevier Science B.V.