Person: Maciá Barber, Enrique Alfonso
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First Name
Enrique Alfonso
Last Name
Maciá Barber
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Física de la Materia Condensada
Identifiers
3 results
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Item Exciton trapping in one-dimensional systems with correlated disorder(Physical Review B, 1994) Domínguez-Adame Acosta, Francisco; Méndez Martín, Bianchi; Sánchez, A.; Maciá Barber, Enrique AlfonsoNumerical investigations of the trapping of Frenkel excitons in one-dimensional lattices with interstitial traps randomly placed in pairs are presented. The probabilities of finding the exciton both in the q = 0 mode P(t) and in any mode Q(t) have been obtained following the numerical approach recently developed by Huber and Ching [Phys. Rev. B 42, 7718 (1990)] for unpaired traps. We have found that the pairing of traps enhances both probabilities at all times, in comparison with lattices containing the same fraction of unpaired traps. We suggest that this behavior is related to the occurrence of larger segments of the lattice that are free of traps, where there exists a major contribution of the slowly decaying modes.Item Excitation decay in one-dimensional disordered-systems with paired traps(Physical Review B, 1995) Sánchez, A.; Domínguez-Adame Acosta, Francisco; Maciá Barber, Enrique AlfonsoIncoherent transport of excitations in one-dimensional disordered lattices with pairs of traps placed at random is studied by numerically solving the corresponding aster equation. Results are compared to the case of lattices with the same concentration of unpaired traps, and it is found that pairing of traps causes a slowdown of the decay rate of both the mean square displacement and the survival probability of excitations. We suggest that this result is due to the presence of larger trap-free segments in the lattices with paired disorder, which mplies that pairing of traps causes less disruption on the dynamics of excitations. In the conclusion we discuss the implications of our work, placing it in a more general context.Item Dynamical phenomena in Fibonacci semiconductor superlattices(Physical Review B, 1996) Díez, E.; Domínguez-Adame Acosta, Francisco; Maciá Barber, Enrique Alfonso; Sánchez, A.We present a detailed study of the dynamics of electronic wave packets in Fibonacci semiconductor superlattices, both in flat band conditions and subject to homogeneous electric fields perpendicular to the layers. Coherent propagation of electrons is described by means of a scalar Hamiltonian using the effective-mass approximation. We have found that an initial Gaussian wave packet is filtered selectively when passing through the superlattice. This means that only those components of the wave packer whose wave numbers belong to allowed subminibands of the fractal-like energy spectrum can propagate over the entire superlattice. The Fourier pattern of the transmitted part of the wave packet presents clear evidences of fractality reproducing those of the underlying energy spectrum. This phenomenon persists even in the presence of unintentional disorder due to growth-induced defects. Finally, we have demonstrated that periodic coherent-field-induced oscillations (Bloch oscillations), which we are able to observe in our simulations of periodic superlattices, are replaced in Fibonacci superlattices by more complex oscillations displaying quasiperiodic signatures, thus shedding more light onto the very peculiar nature of the electronic states in these systems.