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Radchenko T.M.,Linkoping University | Radchenko T.M.,NASU Institute of Physics | Shylau A.A.,Linkoping University | Zozoulenko I.V.,Linkoping University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Numerical calculations of the conductivity of graphene sheets with random and correlated distributions of disorders have been performed using the time-dependent real-space Kubo formalism. The disorder was modeled by the long-range Gaussian potential describing screened charged impurities and by the short-range potential describing neutral adatoms both in the weak and strong scattering regimes. Our central result is that correlation in the spatial distribution for the strong short-range scatterers and for the long-range Gaussian potential do not lead to any enhancement of the conductivity in comparison to the uncorrelated case. Our results strongly indicate that the temperature enhancement of the conductivity reported in the recent study and attributed to the effect of dopant correlations was most likely caused by other factors not related to the correlations in the scattering potential. © 2012 American Physical Society.


De Wijn A.S.,University of Stockholm | Fasolino A.,Radboud University Nijmegen | Filippov A.E.,NASU Institute of Physics | Urbakh M.,Tel Aviv University
Physical Review Letters | Year: 2014

We propose a theoretical model of friction under electrochemical conditions focusing on the interaction of a force microscope tip with adsorbed polar molecules whose orientation depends on the applied electric field. We demonstrate that the dependence of friction force on the electric field is determined by the interplay of two channels of energy dissipation: (i) the rotation of dipoles and (ii) slips of the tip over potential barriers. We suggest a promising strategy to achieve a strong dependence of nanoscopic friction on the external field based on the competition between long-range electrostatic interactions and short-range chemical interactions between tip and adsorbed polar molecules. © 2014 American Physical Society.


Filippov A.E.,NASU Institute of Physics | Popov V.L.,TU Berlin | Urbakh M.,Tel Aviv University
Physical Review Letters | Year: 2011

We propose a model for a description of formation of quasiperiodic nanoscale patterns induced by scratching a surface with an atomic force microscope tip. The simulations demonstrate that the interplay between the developing surface corrugation and the frictional stress produced by the moving tip plays a decisive role in the formation of the regular ripples. Our model reveals the size and shape of the tip as the main factors that determine periodicity and amplitudes of the patterns, and it allows experimental observations to be explained. It is shown that the wear at the nanoscale cannot be explained by conventional macroscopic wear theories. © 2011 American Physical Society.


Pohrt R.,TU Berlin | Popov V.L.,TU Berlin | Filippov A.E.,NASU Institute of Physics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

It was shown earlier that some classes of three-dimensional contact problems can be mapped onto one-dimensional systems without loss of essential macroscopic information, thus allowing for immense acceleration of numerical simulations. The validity of this method of reduction of dimensionality has been strictly proven for contact of any axisymmetric bodies, both with and without adhesion. In, it was shown that this method is valid "with empirical accuracy" for the simulation of contacts between randomly rough surfaces. In the present paper, we compare exact calculations of contact stiffness between elastic bodies with fractal rough surfaces (carried out by means of the boundary element method) with results of the corresponding one-dimensional model. Both calculations independently predict the contact stiffness as a function of the applied normal force to be a power law, with the exponent varying from 0.50 to 0.85, depending on the fractal dimension. The results strongly support the application of the method of reduction of dimensionality to a general class of randomly rough surfaces. The mapping onto a one-dimensional system drastically decreases the computation time. © 2012 American Physical Society.


Grant
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2007.8.0 | Award Amount: 2.29M | Year: 2009

New magneto-transport phenomena have been discovered in magnetic multilayers and are now being optimized for industrial applications, extending the conventional electronics with new functionality. However, most of the current research on magnetic multilayer materials and its device applications rely on conventional equilibrium electron transport. The full potential of nano-structuring, which leads to a broad spectrum of novel non-equilibrium transport phenomena, is therefore not realized. In this research project we will focus on practically unexplored functional principles that can be implemented in nanostructures produced by state-of-the-art lithography and surface manipulation techniques. Our main idea is to use electrically controlled spin currents in highly non-equilibrium regimes with respect to energy and temperature; hence spin-thermo-electronics. The large amount of heat generated in nanoscale devices is today one of the most fundamental obstacles for reducing the size of electronics. In this proposal we turn the problem around by instead using electrically controlled local heating of magnetic nano-circuits to achieve fundamentally new functionality, relevant to several key objectives of the information and communication technology. Particular emphasis will be put on investigating and technologically evaluating the interplay of spin, charge, and heat in magnetic structures of sub-10 nm dimensions. Such structures, although inaccessible by todays lithographic means, are in our view crucial for further miniaturization of electronic devices.

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