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
6 results
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Now showing 1 - 6 of 6
Item A transfer-matrix method for the determination of one-dimensional band structures(Journal of Physics A-Mathematical and General, 1993) Méndez Martín, Bianchi; Domínguez-Adame Acosta, Francisco; Maciá Barber, Enrique AlfonsoWe show that the discretized forms of the Schrodinger and the Dirac equations for an arbitrary potential in one dimension are equivalent to the Poincare map of the corresponding wave equation for an array of delta-function potentials. Therefore, the dynamics of particles in general periodic potentials may be studied by means of an equivalent generalized Kronig-Penney model, in which there exist several delta-function potentials in each unit cell. Taking into account the techniques of dynamical systems, the transfer matrix method is then used in a simple form to compute the energy band edges and the dispersion law inside the allowed bands.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 Fibonacci superlattices of narrow-gap III-V semiconductors(Semiconductor Science and Technology, 1995) Domínguez-Adame Acosta, Francisco; Maciá Barber, Enrique Alfonso; Méndez Martín, Bianchi; Roy, C.L.; Khan, A.We report the theoretical electronic structure of Fibonacci superlattices of narrow-gap III-V semiconductors. The electron dynamics is accurately described within the envelope-function approximation in a two-band model. Quasiperiodicity is introduced by considering two different Ill-V semiconductor layers and arranging them according to the Fibonacci series along the growth direction. The resulting energy spectrum is then found by solving exactly the corresponding effective-mass (Dirac-like) wave equation using tranfer-matrix techniques. We find that a self-similar electronic spectrum can be seen in the band structure. Electronic transport properties of samples are also studied and related to the degree of spatial localization of electronic envelope functions via the Landauer resistance and Lyapunov coefficient. As a working example, we consider type II InAs/GaSb superlattices and discuss in detail our results in this system.Item Electronic-structure of Si delta-doped GaAs in an electric-field(Semiconductor Science and Technology, 1994) Domínguez-Adame Acosta, Francisco; Méndez Martín, Bianchi; Maciá Barber, Enrique AlfonsoThe electron dynamics and the density of states of both single and periodic Si delta-doped GaAs subject to an applied electric field are studied theoretically. The space charge potential due to delta-doping is obtained by means of the semiclassical Thomas-Fermi model. Analysing the change in the density of states introduced by the delta-doping plus the electric field, we observe a set of sharp peaks, corresponding to field-induced localized states, and subsidiary peaks associated with more extended states. Furthermore, we use the inverse participation ratio to evaluate the spatial extent of electron wavefunctions. The number of sharp peaks equals the number of delta-doped layers. In the case of periodically delta-doped samples, the sharp peaks are equally spaced and give rise to Stark ladder resonances.Item Electronic-structure of fibonacci Si δ-doped GaAs(Physics Letters A, 1994) Domínguez-Adame Acosta, Francisco; Maciá Barber, Enrique Alfonso; Méndez Martín, BianchiWe study the electronic structure of a new type of Fibonacci superlattice based on Si delta-doped GaAs. Assuming that delta-doped layers are equally spaced, quasiperiodicity is introduced by selecting two different donor concentrations and arranging them according to the Fibonacci series along the growth direction. The one-electron potential due to delta-doping is obtained by means of the Thomas-Fermi approach. The resulting energy spectrum is then found by solving the corresponding effective-mass wave equation. We find that a self-similar spectrum can be seen in the band structure. Electronic transport properties of samples are also discussed and related to the degree of spatial localization of electronic envelope functions.Item Nonlocal separable potential approach to multicenter interactions(Molecular Physics, 1991) Domínguez-Adame Acosta, Francisco; Méndez Martín, Bianchi; Maciá Barber, Enrique Alfonso; González, M. A.It is shown that nonlocal separable potentials may be used to study bound states of particles in multicentre potentials. The binding energy is obtained in a closed form. The cases of H_2+ ion and polymer chains are discussed in detail and results compared to experimental data.