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Gianaurelio Cuniberti

Publications and source records attributed to Gianaurelio Cuniberti.

100 records · Page 6Linked to original sources

Charge Transport in DNA-Based Devices

Charge migration along DNA molecules has attracted scientific interest for over half a century. Reports on possible high rates of charge transfer between donor and acceptor through the DNA, obtained in the last decade from solution chemistry experiments on large numbers of molecules, triggered a series of direct electrical transport measurements through DNA single molecules, bundles and networks. These measurements are reviewed and presented here. From these experiments we conclude that electrical transport is feasible in short DNA molecules, in bundles and networks, but blocked in long single molecules that are attached to surfaces. The experimental background is complemented by an account of the theoretical/computational schemes that are applied to study the electronic and transport properties of DNA-based nanowires. Examples of selected applications are given, to show the capabilities and limits of current theoretical approaches to accurately describe the wires, interpret the transport measurements, and predict suitable strategies to enhance the conductivity of DNA nanostructures.

cond-mat.mtrl-sci↗

Tight binding description of the STM image of molecular chains

A tight binding model for scanning tunneling microscopy images of a molecule adsorbed on a metal surface is described. The model is similar in spirit to that used to analyze conduction along molecular wires connecting two metal leads and makes it possible to relate these two measurements and the information that may be gleaned from the corresponding results. In particular, the dependence of molecular conduction properties along and across a molecular chain on the chain length, intersite electronic coupling strength and on thermal and disorder effects are discussed and contrasted. It is noted that structural or chemical defects that may affect drastically the conduction along a molecular chain have a relatively modest influence on conduction across the molecular wire in the transversal direction.

cond-mat.mes-hall↗

Anomalous Tien-Gordon scaling in a 1d tunnel junction

We investigate the nonlinear ac transport through a quantum wire with an impurity in the presence of finite range electron-electron interactions. We discuss the influence of the spatial shape of the ac electric field onto transport properties of the system and find that the scaling behavior of the occupation probability of the sidebands depends on the range of the voltage drop.

cond-mat.mes-hall↗

Local fields in nonlinear quantum transport

We investigate the dynamical interplay between currents and electromagnetic fields in frequency-dependent transport through a single-channel quantum wire with an impurity potential in the presence of electron-electron interactions. We introduce and discuss a formalism which allows a self-consistent treatment of currents and electromagnetic fields.

cond-mat.mes-hall↗

Frequency scaling of photo-induced tunneling

The DC current-voltage characteristics, induced by a driving electric field with frequency Omega, of a one dimensional electron channel with a tunnel barrier is calculated. Electron-electron interaction of finite-range is taken into account. For intermediate interaction strengths, the non-linear differential conductance shows cusp-like minima at bias voltages integer multiples of hbar Omega / e that are a consequence of the finite non-zero range of the interaction but are independent of the shape of the driving electric field. However, the frequency-scaling of the photo-induced current shows a cross-over between Omega^{-1} and Omega^{-2}, and depends on the spatial shape of the driving field and the range of the interaction.

cond-mat.mes-hall↗

Correlations in the Bond-Future Market

We analyze the time series of overnight returns for the bund and btp futures exchanged at LIFFE (London). The overnight returns of both assets are mapped onto a one-dimensional symbolic-dynamics random walk: The `bond walk'. During the considered period (October 1991 - January 1994) the bund-future market opened earlier than the btp-future one. The crosscorrelations between the two bond walks, as well as estimates of the conditional probability, show that they are not independent; however each walk can be modeled by means of a trinomial probability distribution. Monte Carlo simulations confirm that it is necessary to take into account the bivariate dependence in order to properly reproduce the statistical properties of the real-world data. Various investment strategies have been devised to exploit the `prior' information obtained by the aforementioned analysis.

cond-mat.stat-mech↗

Volatility in the Italian Stock Market: an Empirical Study

We study the volatility of the MIB30-stock-index high-frequency data from November 28, 1994 through September 15, 1995. Our aim is to empirically characterize the volatility random walk in the framework of continuous-time finance. To this end, we compute the index volatility by means of the log-return standard deviation. We choose an hourly time window in order to investigate intraday properties of volatility. A periodic component is found for the hourly time window, in agreement with previous observations. Fluctuations are studied by means of detrended fluctuation analysis, and we detect long-range correlations. Volatility values are log-stable distributed. We discuss the implications of these results for stochastic volatility modelling.

cond-mat.stat-mech↗

AC-conductance of a quantum wire with electron-electron interaction

The complex ac-response of a quasi-one dimensional electron system in the one-band approximation with an interaction potential of finite range is investigated. It is shown that linear response is exact for this model. The influence of the screening of the electric field is discussed. The complex absorptive conductance is analyzed in terms of resistive, capacitive and inductive behaviors.

cond-mat.mes-hall↗

Coulomb blockade at a tunnel junction between two quantum wires with long-range interaction

The non-linear current-voltage characteristic of a tunnel junction between two Luttinger systems is calculated for an interaction with finite range. Coulomb blockade features are found. The dissipative resistance, the capacitance and the external impedance, which were introduced ad hoc in earlier theories, are obtained in terms of the electron-electron interaction. The frequency dependence of the impedance is given by the excitation spectrum of the electrons.

cond-mat.mes-hall↗