DYNAMICAL LOCALIZATION AND ABSOLUTE NEGATIVE CONDUCTANCE IN AN AC-DRIVEN DOUBLE QUANTUM WELL

We analyze the I-V characteristic of a double quantum well integrated into an antenna and driven by THz radiation. We propose a microscopic model to calculate self-consistently the sequential current including the Coulomb interaction in a mean-field approximation. Additional features in the I-V characteristics appear that depend not only on the frequency and the intensity of the ac field but also on the charge in the wells. We observe dynamical localization and absolute negative conductance in the linear response regime. We compare our calculations with recent experiments in ac-driven double wells. @S0163-1829~97!07720-5# The effect of an ac field on the transport properties of nanostructures has been a subject of increasing interest in the past few years. Recently transport experiments have been performed in semiconductor nanostructures in different ac fields. Photoassisted current through a double barrier ~DB! irradiated with FIR light shows 1 additional features which can be explained in terms of the coupling of different electronic states induced by the electromagnetic field. 2 The effect of an ac potential on the conductance and current in quantum dots 3,4 in superlattices ~SL’s !, 5 and in double quantum wells ~DQW’s !~ Ref. 6! has been measured and new physical features, such as dynamical localization ~DL! and absolute negative conductance ~ANC!, have been observed. 5 Also Rabi transitions between discrete states and electron pumping in double quantum dots ~DQD’s ! have been analyzed within the Keldysh formalism. 7 In this work we propose a model for analyzing the timeaverage current in a triple barrier ~TB! integrated into an antenna and driven by THz radiation. In this configuration, the irradiated antenna produces an oscillatory signal between the left and right lead, i.e., a time-dependent bias drops between the emitter and collector. In order to account for scattering due to roughness at the interfaces, phonons, or impurities, we analyze sequential tunnel: we calculate the current from the emitter to the left well Je,1 , from the left well to the right well J 1,2 , and from the right well to the collector J 2,c . Current conservation determinates the Fermi energies in the wells and the sequential current. The effect of electron-electron interaction in these quasi-3D structures can be treated as a perturbation to the noninteracting system within a mean field approximation. 8,9 The charge accumulated in the wells produces an additional electrostatic potential which modifies their electronic structure, transmission coefficient, and current. We solve self-consistently the