Wannier-Stark effect on surface states

A recursive Green-function (RGF) technique is used to study the surface states of an electrified solid. The concatenating nature of the method leads to a continued-fraction form of the RGF, which can be expressed as a ratio of Bessel functions. The surface density of states (SDOS), derived from the RGF, reveals a quasi-Stark-ladder distribution of the energy levels at the surface atom. The dependence of the SDOS on the applied field and surface perturbation parameters is discussed.     

Surface states in electrochemisorption

The recursive Green function (RGF) method is used to obtain the surface and adatom RGFs for an electrified substate. The electrochemisorption (ECS) process is described, by invoking the Anderson–Newns (AN) model, whereby a self-consistent treatment of the ECS energy and charge transfer is provided. The role of the electric field, and the presence of surface states (SS), in governing magnetic and non-magnetic ECS is discussed in the case of H–Cr.     

Free energy of a Lovelock holographic superconductor

We study thermodynamics of black hole solutions in Lanczos–Lovelock anti-de Sitter gravity in \(d+1\) dimensions coupled to nonlinear electrodynamics and a Stückelberg scalar field. This class of theories is used in the context of gauge/gravity duality to describe a high-temperature superconductor in \(d\) dimensions. A larger number of coupling constants in the gravitational side is necessary to widen the domain of validity of physical quantities in dual quantum field theory (QFT). We regularize the gravitational action and find the finite conserved quantities for a planar black hole with scalar hair. Then we derive the quantum statistical relation in the Euclidean sector of the theory, and we obtain the exact formula for the free energy of the superconductor in the holographic QFT. Our result is analytic and it includes the effects of backreaction of the gravitational field. We further discuss on how this formula could be used to analyze second order phase transitions through the discontinuities of the free energy, in order to classify holographic superconductors in terms of the parameters in the theory.     

Coulomb explosion patterns of fast C60 clusters in solids

The molecular dynamics method is used to simulate Coulomb explosion of fast C60 ion clusters in an Al target, taking into account dynamical screening of interionic interactions by the electron gas of the target. It is found that the wake forces in the medium are strong enough, depending on cluster speed, to stabilize the whole cluster against Coulomb explosion, or to compress the trailing part of the cluster, for prolonged times of penetration through the target. This is encouraging news for such cluster-ion beams applications where massive energy depositions in small volumes of targets are desired.     

Préparation de copolymères greffés par voie cationique—III. Structure et propriétés mécaniques des copolymères

Graft copolymers obtained by cationic grafting of indene on chlorinated butyl rubber have comblike structures. Their mechanical properties can be related to the number of branches per backbone. They partly retain these properties up to 100%. Copolymers prepared by grafting on ethylene-propylene-diene terpolymers have less well defined structures and poor mechanical properties, even at room temperature.