4,356 research outputs found
Effective models for charge transport in DNA nanowires
The rapid progress in the field of molecular electronics has led to an
increasing interest on DNA oligomers as possible components of electronic
circuits at the nanoscale. For this, however, an understanding of charge
transfer and transport mechanisms in this molecule is required. Experiments
show that a large number of factors may influence the electronic properties of
DNA. Though full first principle approaches are the ideal tool for a
theoretical characterization of the structural and electronic properties of
DNA, the structural complexity of this molecule make these methods of limited
use. Consequently, model Hamiltonian approaches, which filter out single
factors influencing charge propagation in the double helix are highly valuable.
In this chapter, we give a review of different DNA models which are thought to
capture the influence of some of these factors. We will specifically focus on
static and dynamic disorder.Comment: to appear in "NanoBioTechnology: BioInspired device and materials of
the future". Edited by O. Shoseyov and I. Levy. Humana Press (2006
Charge transport in a nonlinear, three--dimensional DNA model with disorder
We study the transport of charge due to polarons in a model of DNA which
takes in account its 3D structure and the coupling of the electron wave
function with the H--bond distortions and the twist motions of the base pairs.
Perturbations of the ground states lead to moving polarons which travel long
distances. The influence of parametric and structural disorder, due to the
impact of the ambient, is considered, showing that the moving polarons survive
to a certain degree of disorder. Comparison of the linear and tail analysis and
the numerical results makes possible to obtain further information on the
moving polaron properties.Comment: 9 pages, 2 figures. Proceedings of the conference on "Localization
and energy transfer in nonlinear systems", June 17-21, 2002, San Lorenzo de
El Escorial, Madrid, Spain. To be publishe
Nonlinear charge transport mechanism in periodic and disordered DNA
We study a model for polaron-like charge transport mechanism along DNA
molecules with emphasis on the impact of parametrical and structural disorder.
Our model Hamiltonian takes into account the coupling of the charge carrier to
two different kind of modes representing fluctuating twist motions of the base
pairs and H-bond distortions within the double helix structure of
DNA. Localized stationary states are constructed with the help of a
nonlinear map approach for a periodic double helix and in the presence of
intrinsic static parametrical and/or structural disorder reflecting the impact
of ambient solvent coordinates. It is demonstrated that charge transport is
mediated by moving polarons respectively breather compounds carrying not only
the charge but causing also local temporal deformations of the helix structure
through the traveling torsion and bond breather components illustrating the
interplay of structure and function in biomolecules.Comment: 23 pages, 13 figure
Modeling molecular conduction in DNA wires: Charge transfer theories and dissipative quantum transport
Measurements of electron transfer rates as well as of charge transport
characteristics in DNA produced a number of seemingly contradictory results,
ranging from insulating behaviour to the suggestion that DNA is an efficient
medium for charge transport. Among other factors, environmental effects appear
to play a crucial role in determining the effectivity of charge propagation
along the double helix. This chapter gives an overview over charge transfer
theories and their implication for addressing the interaction of a molecular
conductor with a dissipative environment. Further, we focus on possible
applications of these approaches for charge transport through DNA-based
molecular wires
Hitchhiking transport in quasi-one-dimensional systems
In the conventional theory of hopping transport the positions of localized
electronic states are assumed to be fixed, and thermal fluctuations of atoms
enter the theory only through the notion of phonons. On the other hand, in 1D
and 2D lattices, where fluctuations prevent formation of long-range order, the
motion of atoms has the character of the large scale diffusion. In this case
the picture of static localized sites may be inadequate. We argue that for a
certain range of parameters, hopping of charge carriers among localization
sites in a network of 1D chains is a much slower process than diffusion of the
sites themselves. Then the carriers move through the network transported along
the chains by mobile localization sites jumping occasionally between the
chains. This mechanism may result in temperature independent mobility and
frequency dependence similar to that for conventional hopping.Comment: a few typos correcte
Dissipative Effects in the Electronic Transport through DNA Molecular Wires
We investigate the influence of a dissipative environment which effectively
comprises the effects of counterions and hydration shells, on the transport
properties of short \DNA wires. Their electronic structure is captured by a
tight-binding model which is embedded in a bath consisting of a collection of
harmonic oscillators. Without coupling to the bath a temperature independent
gap opens in the electronic spectrum. Upon allowing for electron-bath
interaction the gap becomes temperature dependent. It increases with
temperature in the weak-coupling limit to the bath degrees of freedom. In the
strong-coupling regime a bath-induced {\it pseudo-gap} is formed. As a result,
a crossover from tunneling to activated behavior in the low-voltage region of
the - characteristics is observed with increasing temperature. The
temperature dependence of the transmission near the Fermi energy, , manifests an Arrhenius-like behavior in agreement with recent transport
experiments. Moreover, shows a weak exponential dependence on
the wire length, typical of strong incoherent transport. Disorder effects smear
the electronic bands, but do not appreciably affect the pseudo-gap formation
Quantum transport through a DNA wire in a dissipative environment
Electronic transport through DNA wires in the presence of a strong
dissipative environment is investigated. We show that new bath-induced
electronic states are formed within the bandgap. These states show up in the
linear conductance spectrum as a temperature dependent background and lead to a
crossover from tunneling to thermal activated behavior with increasing
temperature. Depending on the strength of the electron-bath coupling, the
conductance at the Fermi level can show a weak exponential or even an algebraic
length dependence. Our results suggest a new environmental-induced transport
mechanism. This might be relevant for the understanding of molecular conduction
experiments in liquid solution, like those recently performed on poly(GC)
oligomers in a water buffer (B. Xu et al., Nano Lett 4, 1105 (2004)).Comment: 5 pages, 3 figure
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