Abstract

Twelve years ago, Dunlap and Kenkre studied theoretically the problem of electron dynamics in a Bloch band driven by an AC electric field. They found the surprising resuit that DC transport of the electrons can be completely shut off when the strength of the AC field takes some special values.¹ This effect was later found to be associated with a collapse of the Bloch bands in a Floquet analysis of the quasi-energy spectrum.² The suppression of electron transport has indeed been observed on a superlattice driven by a Terahertz free-electron laser,³ but it was interpreted as the inhibition of inter-well tunneling rather than that of Bloch transport, because it is not clear if quantum coherence can be maintained over a distance of more than two wells.

© 1999 Optical Society of America