Localization of two interacting electrons in quantum dot arrays driven by an ac field

We investigate the dynamics of two interacting electrons moving in a one-dimensional array of quantum dots under the influence of an ac field. We show that the system exhibits two distinct regimes of behavior, depending on the ratio of the strength of the driving field to the interelectron Coulomb repulsion. When the ac-field dominates, an effect termed coherent estruction of tunneling occurs at certain frequencies, in which transport along the array is suppressed. In the other, weak-driving, regime we find the surprising result that the two electrons can bind into a single composite particle—despite the strong Coulomb repulsion between them— which can then be controlled by the ac field in an analogous way. We show how calculation of the Floquet quasienergies of the system explains these results, and thus how ac fields can be used to control the localization of interacting electron systems.