Person: MaciĆ” Barber, Enrique Alfonso
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First Name
Enrique Alfonso
Last Name
MaciĆ” Barber
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias FĆsicas
Department
FĆsica de Materiales
Area
FĆsica de la Materia Condensada
Identifiers
58 results
Search Results
Now showing 1 - 10 of 58
Item Electronic structure and transport properties of double-stranded Fibonacci DNA(Physical review B, 2006) MaciĆ” Barber, Enrique AlfonsoWe consider a class of synthetic DNA molecules based on a quasiperiodic arrangement of their constituent nucleotides. Making use of a two-step renormalization scheme the double-stranded DNA molecule is modeled in terms of a one-dimensional effective Hamiltonian, which includes contributions from the nucleobase system, the sugar-phosphate backbone, and the environment. Analytical results for the energy spectrum structure and Landauer conductance of Fibonacci DNA approximants are derived and compared with those corresponding to periodic polyGACT-polyCTGA chains. The main effect of quasiperiodic order is the emergence of a highly fragmented energy spectrum, introducing a characteristic low-energy scale in the electronic structure of aperiodic DNA chains. The presence of a series of high-conductance peaks in the transmission spectra of Fibonacci approximants indicates the existence of extended states in these systems. These results open perspectives for experimental work in nanodevices based on synthetic DNA.Item Aperiodic crystals in biology(Journal of physics-condensed matter, 2022) MaciĆ” Barber, Enrique AlfonsoBiological systems display a broad palette of hierarchically ordered designs spanning over many orders of magnitude in size. Remarkably enough, periodic order, which profusely shows up in non-living ordered compounds, plays a quite subsidiary role in most biological structures, which can be appropriately described in terms of the more general aperiodic crystal notion instead. In this topical review I shall illustrate this issue by considering several representative examples, including botanical phyllotaxis, the geometry of cell patterns in tissues, the morphology of sea urchins, or the symmetry principles underlying virus architectures. In doing so, we will realize that albeit the currently adopted quasicrystal notion is not general enough to properly account for the rich structural features one usually finds in biological arrangements of matter, several mathematical tools and fundamental notions belonging to the aperiodic crystals science toolkit can provide a useful modeling framework to this end.Item Fluorescence decay in aperiodic Frenkel lattices(Physical Review B, 1996) DomĆnguez-Adame Acosta, Francisco; MaciĆ” Barber, Enrique AlfonsoWe study motion and capture of excitons in self-similar linear systems in which interstitial traps are arranged according to an aperiodic sequence, focusing our attention on Fibonacci and Thue-Morse systems as canonical examples. The decay of the fluorescence intensity following a broadband pulse excitation is evaluated by solving the microscopic equations of motion of the Frenkel exciton problem. We find that the average decay is exponential and depends only on the concentration of traps and the trapping rate. In addition, we observe small-amplitude oscillations coming from the coupling between the low-lying mode and a few high-lying modes through the topology of the lattice. These oscillations are characteristic of each particular arrangement of traps and they are directly related to the Fourier transform of the underlying lattice. Our predictions then can be used to determine experimentally the ordering of traps.Item Electronic transport and thermopower in aperiodic DNA sequences(Modern physics letters B, 2004) Roche, Stephan; MaciĆ” Barber, Enrique AlfonsoA detailed study of charge transport properties of synthetic and genomic DNA sequences is reported. Genomic sequences of the Chromosome 22, lambda-bacteriophage, and D1s80 genes of Human and Pygmy chimpanzee are considered in this work, and compared with both periodic and quasiperiodic (Fibonacci) sequences of nucleotides. Charge transfer efficiency is compared for all these different sequences, and large variations in charge transfer efficiency, stemming from sequence-dependent effects, are reported. In addition, basic characteristics of tunneling currents, including contact effects, are described. Finally, the thermoelectric power of nucleobases connected in between metallic contacts at different temperatures is presented.Item Erratum: Suppression of localization in kronig-penney models with correlated disorder (Vol. 49, PG 147, 1994)(Physical review B, 1994) SĆ”nchez, Angel; MaciĆ” Barber, Enrique Alfonso; DomĆnguez-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 Charge transfer in DNA: effective Hamiltonian approaches(Zetischrift fur kristallographie, 2009) MaciĆ” Barber, Enrique AlfonsoAperiodic order plays a very significant role in biology, as it determines most informative content of genomes. Amongst the various physical, chemical or biological phenomena that might be inferred from sequence correlations, charge transfer properties deserve particular attention. Indeed, the nature of DNA-mediated charge migration has been related to the understanding of damage recognition process, protein binding, or with the task of engineering biological processes (e.g. designing nanoscale sensing of genomic mutations), opening new challenges for emerging nanobiotechnologies. Nevertheless, the solution of Schrodinger's equation with a potential that is given by a one-dimensional array of the double-stranded DNA remains as a main open theme in solid state physics of biological macromolecules. In this contribution, I will shortly review several approaches introduced during the last few years in order to describe charge transfer migration in DNA in terms of tight-binding effective Hamiltonians.Item May quasicrystals be good thermoelectric materials?(Applied physics letters, 2000) MaciĆ” Barber, Enrique AlfonsoWe present a theoretical analysis of quasicrystals (QCs) as potential thermoelectric materials. We consider a self-similar density of states model and extend the framework introduced in [G. D. Mahan and J. O. Sofo, Proc. Natl. Acad. Sci. U.S.A. 93, 7436 (1996)] to systems exhibiting correlated features in their electronic structure. We show that relatively high values of the thermoelectric figure of merit, ranging from 0.01 up to 1.6 at room temperature, may be expected for these systems. We compare our results with available experimental data on transport properties of QCs and suggest some potential candidates for thermoelectric applications.Item Incoherent exciton trapping in self-similar aperiodic lattices(Physical review B, 1995) DomĆnguez-Adame Acosta, Francisco; MaciĆ” Barber, Enrique Alfonso; SĆ”nchez, AngelIncoherent exciton dynamics in one-dimensional perfect lattices with traps at sites arranged according to aperiodic deterministic sequences is studied. We focus our attention on Thue-Morse and Fibonacci systems as canonical examples of self-similar aperiodic systems. Solving numerically the corresponding master equation we evaluate the survival probability and the mean-square displacement of an exciton initially created at a single site. Results are compared to systems of the same size with the same concentration of traps randomly as well as periodically distributed over the whole lattice. Excitons progressively extend over the lattice on increasing time and, in this sense, they act as a probe of the particular arrangements of traps in each system considered. The analysis of the characteristic features of their time decay indicates that exciton dynamics in self-similar aperiodic arrangements of traps is quite close to that observed in periodic ones, but di8'ers significantly from that corresponding to random lattices. We also report on characteristic features of exciton motion suggesting that Fibonacci and Thue-Morse orderings might be clearly observed by appropriate experimental measurements. In the conclusions we comment on the implications of our work on the way towards a unified theory of the ordering of matter.Item Effects of the electronic structure on the dc conductance of Fibonacci superlattices(Physical Review B, 1994) MaciĆ” Barber, Enrique Alfonso; DomĆnguez-Adame Acosta, Francisco; SĆ”nchez, AngelWe derive a discrete Hamiltonian describing a Fibonacci superlattice in which the electronic potential is taken to be an array of equally spaced delta potentials, whose strengths modulate the chemical composition in the growth direction. In this model both diagonal and off-diagonal elements of the Hamiltonian matrix become mutually related through the potential strengths. The corresponding energy spectrum and related magnitudes, such as the Lyapunov coefficient, transmission coefficient, and Landauer resistance, exhibit a highly fragmented, self-similar nature. We investigate the influence of the underlying spectrum structure on the dc conductance at different temperatures obtaining analytical expressions which relate special features of the dc conductance with certain parameters that characterize the electronic spectrum of Fibonacci superlattices.Item Long range correlations in DNA: scaling properties and charge transfer efficiency(Physical review letters, 2003) Roche, S.; Bicout, D.; MaciĆ” Barber, Enrique Alfonso; Kats, E.We address the relation between long-range correlations and charge transfer efficiency in aperiodic artificial or genomic DNA sequences. Coherent charge transfer through the highest occupied molecular orbital states of the guanine nucleotide is studied using the transmission approach, and the focus is on how the sequence-dependent backscattering profile can be inferred from correlations between base pairs.