RANDOM LATTICES IN COMBINED AC AND DC ELECTRIC-FIELDS - ANDERSON VS WANNIER-STARK LOCALIZATION

Employing a single-band tight-binding model with random diagonal disor der, we study localization of quasi-energy states in the presence of b oth static and resonant oscillating electric fields. A characteristic minimum strength of the a.c. field is required for effective destructi on of the localization induced by the d.c. field. The numerically dete rmined dependence of this characteristic a.c. field amplitude on the d isorder strength confirms that the localization of wave packets in dis ordered lattices under simultaneous d.c. and resonant a.c. bias is ent irely analogous to the familiar Anderson mechanism in the absence of e xternal fields, but with field-''renormalized'' quasi-energy bands pla ying the role of energy bands in the field-free case.