Heteroestruturas de semicondutores na presença de campos AC intensos

AUTOR(ES)

Pablo Hector Rivera Riofano

DATA DE PUBLICAÇÃO

1998

RESUMO

The study of coupling of the electronic structure of a semiconductor heterostructure with strong AC fields, is the main purpose of the present work. The interaction of the electronic structure of a heterostructure with an AC field of determined frequency is given by a time-independent Hamiltonian which replaces a semiclassic time- dependent Hamiltonian. The heterostructure electronic structure is described by a heuristic model based on the tight-binding approximation, considering only nearest neighbors. We follow the evolution of the dressed minibands, non perturbatively, in a quasienergies esquem on the Brillouin zones. Firstly, observing the validity of the model, we simulate the dressed miniband of a superlattice and the collapses produced by the variation of the AC field and comparing these results with others that we found in the literature. Secondly, we simulate two coupling and dressed superlattice minibands -obtained with two quantum wells of alternate and different width- from the high frequency regime where the minibands are strongly coupled- to other regime of low frequency, where the minibands are isolated. In the transition between both regimes, there is a competition between resonances due to AC Stark shifts and the collapsing of dressed dimers ( two wells with different width). When the ratio of the gap of minibands and the foton energy is an integer number, ocurs collapses of the miniband gap (similarly to a field induced like insulator-metal transition). Finally, we simulate the electronic structure of a bidimensional array of quantum dots or antidots under a perpendicular magnetic field and two paralel AC fields. The quasienergies spectra show an autosimilar structure when there are frequencies commesurability. Also is observed the crossing of ground state induced by the AC field

ASSUNTO(S)

poços quanticos semicondutores superestrutura como material heteroestruturas campos eletromagneticos

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