Person: Domínguez-Adame Acosta, Francisco
Loading...
First Name
Francisco
Last Name
Domínguez-Adame Acosta
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Física de la Materia Condensada
Identifiers
181 results
Search Results
Now showing 1 - 10 of 181
Item Absence of extended states in a ladder model of DNA(Physical Review B, 2007) Díaz García, Elena; Sedrakyan, A.; Sedrakyan, D.; Domínguez-Adame Acosta, FranciscoWe consider a ladder model of DNA for describing carrier transport in a fully coherent regime through finite segments. A single orbital is associated to each base, and both interstrand and intrastrand overlaps are considered within the nearest-neighbor approximation. Conduction through the sugar-phosphate backbone is neglected. We study analytically and numerically the spatial extend of the corresponding states by means of the Landauer and Lyapunov exponents. We conclude that intrinsic-DNA correlations, arising from the natural base pairing, does not suffice to observe extended states, in contrast to previous claims.Item Anderson transition in low-dimensional disordered systems driven by long-range nonrandom hopping(Physical Review Letters, 2003) Rodriguez, A.; Malyshev, Andrey; Sierra, G.; Martin-Delgado Alcántara, Miguel Ángel; Rodriguez-Laguna, J.; Domínguez-Adame Acosta, FranciscoThe single-parameter scaling hypothesis predicts the absence of delocalized states for noninteracting quasiparticles in low-dimensional disordered systems. We show analytically, using a supersymmetric method combined with a renormalization group analysis, as well as numerically that extended states may occur in the one- and two-dimensional Anderson model with a nonrandom hopping falling off as some power of the distance between sites. The different size scaling of the bare level spacing and the renormalized magnitude of the disorder seen by the quasiparticles finally results in the delocalization of states at one of the band edges of the quasiparticle energy spectrum.Item Suppression of localization in kronig-penney models with correlated disorder(Physical Review B, 1994) Sáchez, A.; Maciá Barber, Enrique Alfonso; Domínguez-Adame Acosta, FranciscoWe consider the electron dynamics and transport properties of one-dimensional continuous models with random, short-range correlated impurities. We develop a generalized Poincare map formalism to cast the Schrodinger equation for any potential into a discrete set of equations, illustrating its application by means of a specific example. We then concentrate on the case of a Kronig-Penney model with dimer impurities. The previous technique allows us to show that this model presents infinitely many resonances (zeroes of the reflection coefficient at a single dimer) that give rise to a band of extended states, in contradiction with the general viewpoint that all one-dimensional models with random potentials support only localized states. We report on exact transfer-matrix numerical calculations of the transmission coefFicient, density of states, and localization length for various strengths of disorder. The most important conclusion so obtained is that this kind of system has a very large number of extended states. Multifractal analysis of very long systems clearly demonstrates the extended character of such states in the thermodynamic limit. In closing, we brieBy discuss the relevance of these results in several physical contexts.Item Impact of electron-vibron interaction on the bound states in the continuum(Physics letters A, 2015) Álvarez, C; Domínguez-Adame Acosta, Francisco; Orellana, P. A.; Díaz García, ElenaWe investigate the nonequilibrium transport properties of a coupled quantum dot system connected in parallel to two leads, including electron-vibron interaction. It is known that in the absence of interaction the system supports a bound state in the continuum. This state is revealed as a Fano antiresonance in the transmission when the energy levels of the dots are detuned. Using the Keldysh nonequilibrium Green's function formalism, we find that the occurrence of the Fano antiresonance arises even if the electronvibration interaction is taken into account. We also examine the impact of the coupling to the leads in the linear response of the system. We conclude that the existence of bound states in the continuum in coupled quantum dot systems is a robust phenomenon, opening the possibility of its observation in experiments.Item Scattering of massless Dirac particles by oscillating barriers in one dimension(Physics letters A, 2014) González-Santander de la Cruz, Clara; Domínguez-Adame Acosta, Francisco; Fuentevilla, c. H.; Díez, E.We study the scattering of massless Dirac particles by oscillating barriers in one dimension. Using the Floquet theory, we find the exact scattering amplitudes for time-harmonic barriers of arbitrary shape. In all cases the scattering amplitudes are found to be independent of the energy of the incoming particle and the transmission coefficient is unity. This is a manifestation of the Klein tunneling in time-harmonic potentials. Remarkably, the transmission amplitudes for arbitrary sharply-peaked potehtials also become independent of the driving frequency. Conditions for which barriers of finite width can be replaced by sharply-peaked potentials are discussed.Item Motional narrowing effect in certain random binary lattices(Physics Letters A, 2000) Domínguez-Adame Acosta, FranciscoWe present a model for a class of random binary lattices by introducing a one-dimensional system where impurities are placed in one sublattice while host atoms lie on the other sublattice. The source of disorder is the stochastic fluctuation of the impurity energy from site to site. We study the optical absorption spectra and the peculiarities of the motional narrowing effect at the band edges for perturbative and nonperturbative degrees of disorder. Analytical results agree well with numerical simulations.Item Electronic states in graded-gap junctions with band inversion(Physics Letters A, 1995) Domínguez-Adame Acosta, FranciscoWe theoretically study electronic states in graded-gap junctions of IV-VI compounds with band inversion. Using a two-band model within the k . p approximation and assuming that the gap and the gap centre present linear profiles, we demonstrate the existence of a set of localized states along the growth direction with a discrete energy spectrum. The envelope functions are found to be a combination of harmonic oscillator eigenfunctions, and the corresponding energy levels are proportional to the square root of the quantum number. The level spacing can be directly controlled by varying the structure thickness.Item Numerical study of the localization length critical index in a network model of plateau-plateau transitions in the quantum hall effect(Physical Review Letters, 2011) Amado, M.; Malyshev, Andrey; Sedrakyan, A.; Domínguez-Adame Acosta, FranciscoWe calculate numerically the localization length critical index within the Chalker-Coddington model of the plateau-plateau transitions in the quantum Hall effect. We report a finite-size scaling analysis using both the traditional power-law corrections to the scaling function and the inverse logarithmic ones, which provided a more stable fit resulting in the localization length critical index v = 2.616 +/- 0.014. We observe an increase of the critical exponent v with the system size, which is possibly the origin of discrepancies with early results obtained for smaller systems.Item Detection of oxygen-depleted zones in Yba_2Cu_3O_(7—x )by Luminescence(Physica Status Solidi A-Applications and Materials Science, 1993) Remón, A.; García, J. A.; Gómez, P.; Piqueras de Noriega, Javier; Domínguez-Adame Acosta, FranciscoItem Excitation optical-absorption in self-similar aperiodic lattices(Physical Review B, 1994) Maciá Barber, Enrique Alfonso; Domínguez-Adame Acosta, FranciscoExciton optical absorption in self-similar aperiodic one-dimensional systems is considered, focusing our attention on Thue-Morse and Fibonacci lattices as canonical examples. The absorption line shape is evaluated by solving the microscopic equations of motion of the Frenkel-exciton problem on the lattice, in which on-site energies take on two values, according to the Thue-Morse or Fibonacci sequences. Results are compared to those obtained in random lattices with the same stoichiometry and size. We find that aperiodic order causes the occurrence of well-de6ned characteristic features in the absorption spectra, which clearly di8'er from the case of random systems, indicating a most peculiar exciton dynamics. The origin of all the absorption lines is assigned by considering the self-similar aperiodic lattices as composed of two-center blocks, within the same spirit of the renormalization group ideas.