ELSEVIER Surface Science 361/362 (1996) 217-221 surface science Resonant tunneling in time-dependent fields through laterally confined double barriers Ram6n Aguado *, Jes6s Iflarrea, Gloria Platero Institute de Ctencta de Materiales (CSIC) and Departamento de Fistca de la Materia Condensada C-III, Untversidad Autonoma, Cantoblanco, E-28049 Madrid, Spain Received 23 June 1995; azcepted for publication 26 September 1995 Almract We ~.alyze the tunneling current through resonant heterostruetures in the presence of a time-dependent field. We compare two different cases: an AC potential where the external field is position-dependent through the heterostruetu~ versus the case where an electromagnetic field irrAdiAtes homogeneously the whole sample. While in the presence of an AC potential the tunneling takes place mainly through photo sidebands, in the case of homogeneous ilhml/nation the main effective tunneling channetq correspond to the coupling between different electronic states due to photon absorption and emission. The differeace in the tunneling mechanisms between these configurations is strongly reflected in the transmission and current, which present different features in both cases. In order to analyze these effects, we have obtained the transition probab~ity for resonant coherent tunneling in terms of the Green's function of the system. We have appfied this model to analyze the effect of light in the current steps which are present in a laterally confined double barrier where the Coulomb interaction is considered in a mean field approximation. Keywords: Tunneling In recent years several works have been devoted to analyzing the effect of a time-dependent field on the transport properties of resonant hetero- structures. However, there is not yet a systematic discussion of the different experimental fituations corresponding to an AC potential applied between the left and right leads, and which implies a position-dependent dephasing of the external field on the sample, and the case where the whole sample is homogeneously /lh~minated, i.e., where the electron-photon coupling depends on position solely through the momentum matrix elements [1]. In spite of the increasing interest in this * Corresponding author, e-mail: ~hm-noni~emm csic, es field, most of the theoretical work has been done considering an AC potential but the experimental information includes both different configurations. Both situations, however, are physically different because the effective tunneling channels for the flowing of current are different in both cases. In this work we have extended the generalized transfer Hamiltonian (GTH) [2], which allows analysis of the coherent tunneling, to obtain the transition probability in the presence of a time-dependent potential in the two configurations discussed above. We analyze first the effect of an AC field applied just to the left and right leads with a dephasing of ~ between them. In this case the Hamiltonian is such that [3,4] the AC potential 0039-6028/96/$15.00 Copyright O 1996 Elsevier Science B.V. All rights reserved PII S0039-6028 (96) 00388-3