Abstract: Thin superconducting films can exhibit negative magnetoresistance when an in-plane external magnetic field is aligned parallel with the transport current. We explain this effect as due to appearance of parallel vortices in the plain of the film at the first critical magnetic field H-c1 which leads to an enhancement of the superconducting properties and impedes the motion of the current induced perpendicular vortices. Our theoretical results are based on a numerical solution of the time-dependent and stationary 3D Ginzburg-Landau equations.

Abstract: Here we summarize results from our study of the critical depinning current J(c) versus the applied magnetic flux Phi, for: (i) quasiperiodic (QP) one-dimensional (1D) chains and (ii) 2D arrays of pinning centers placed on the nodes of a five-fold Penrose lattice. In 1D QP chains, the peaks in J(c)(Phi) are determined by a sequence of harmonics of the long and short segments of the chain. The critical current J(c)(Phi) has a remarkable self-similarity. In 2D QP pinning arrays, we predict analytically and numerically the main features of J(c)(Phi), and demonstrate that the Penrose lattice of pinning sites provides an enormous enhancement of J(c)(Phi), even compared to triangular and random pinning site arrays. This huge increase in J(c)(Phi) could be useful for applications. (c) 2005 Elsevier B.V. All rights reserved.

Abstract: Cyclotron resonance (CR) of the electrons accumulated at sheets with heavy Si doping in InSb were observed using far infrared radiation. The angular dependence of the CR follows closely the 1/cos theta behaviour with some small deviations at high angles attributed to coupling between subbands. From the effective mass of the lowest subband, which is found to be 0.027m(o), the bottom of the lowest subband was determined to lie 125 meV below the Fermi level.

Abstract: Magnet0transport measurements in pulsed fields up to 46 T and at temperatures between 1.4 and 210 K have been performed on thin semimetallic epitaxial layers of Sc1-xErxAs buried inside insulating GaAs. A consistent description is obtained of the magnetic field dependence of the Hall resistance and the different frequencies of the Shubnikov-de Hass oscillations.

Abstract: It is well-known that the Ginzburg-Landau (GL) theory is a reliable and powerful theoretical tool to investigate the magnetic response of a superconducting state. However, in its standard form, this approach is not applicable to atomically uniform nano-thin superconducting films which are effective multiband superconductors. Here we discuss a relevant generalization of the GL theory, focusing on the underlying intraband-pairing approximation. (C) 2014 Elsevier B.V. All rights reserved.

Abstract: We study the effect of a hydrogen atom on the thermal stability of a trapped CH3 molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH3 molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH3 molecule. We also studied the effect of the CH3-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH3-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH3 molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules. (C) 2014 Elsevier B.V. All rights reserved.

Abstract: The transition Fm (3) over bar m -->Pa (3) over bar in solid C-60 is driven by the condensation of orientational modes belonging to X-5(+) irreducible representations (irreps) of Fm (3) over bar m. Taking into account irreps up to the manifold l = 12, we have studied the primary and secondary orientational order parameters loops). We have numerically solved the coupled molecular field equations for these oops and calculated the temperature dependence of Bragg reflection intensities. (C) 1998 Elsevier Science B.V. All rights reserved.