Ryszard Gonczarek

Radius dependent shift in surface plasmon frequency in large metallic nanospheres: Theory and experiment

Theoretical description of oscillations of electron liquid in large metallic nanospheres (with radius of few tens of nanometer) is formulated within random-phase-approximation semiclassical scheme in jellium model with retardation included via Lorentz friction. Spectrum of plasmons is determined including both surface and volume type excitations. It is demonstrated that only surface plasmons of dipole type can be excited by homogeneous dynamical electric field. The Lorentz friction due to irradiation of electromagnetic wave by plasmon oscillations is analyzed with respect to the sphere dimension. The resulting shift in resonance frequency turns out to be strongly sensitive to the sphere radius. The form of electromagnetic (e-m) response of the system of metallic nanospheres embedded in the dielectric medium is found. The theoretical predictions are verified by a measurement of extinction of light due to plasmon excitations in nanosphere colloidal water solutions, for Au and Ag metallic components with rad...

Surface and volume plasmons in metallic nanospheres in a semiclassical RPA-type approach: Near-field coupling of surface plasmons with the semiconductor substrate

The random-phase-approximation semiclassical scheme for description of plasmon excitations in large metallic nanospheres, with radius range 10-60 nm, is formulated in an all-analytical version. The spectrum of plasmons is determined including both surface and volume type excitations and their mutual connections. The various channels for damping of surface plasmons are evaluated and the relevant resonance shifts are compared with the experimental data for metallic nanoparticles of different size located in dielectric medium or on the semiconductor substrate. The strong enhancement of energy transfer from the surface plasmon oscillations to the substrate semiconductor is explained in the regime of a near-field coupling in agreement with recent experimental observations for metallically nanomodified photo-diode systems.

Enhancement of critical temperature of superconductors implied by the local fluctuation of EDOS

Abstract Applying the formalism developed for the generalized gap equation of BCS type, the critical temperature and heat capacity leap at the phase transition point between the superconducting and normal state are derived. The calculations are carried out when the fluctuation of the electronic density of states in the Fermi surface vicinity is included. Assuming that the EDOS has the Lorentzian form superimposed symmetrically near the Fermi surface on the constant background, it is shown that the critical temperature enhances significantly even for negligible modification of quasiparticle concentration. The disclosed effects can be interpreted in terms of the Van Hove scenario.

Valuation of characteristic ratios for high-Tc superconductors with anisotropic gap in the conformal transformation method

The application of a method of conformal-like transformation of the two-dimensional momentum space is presented and discussed with regard to two-dimensional anisotropic superconductors. A new function, the kernel of the density of states, and some integral formulae are derived, interpreted and studied for a few specific cases. Evidences for the incompatibility between the Van Hove scenario and the conformal transformation method with respect to a couple of characteristic ratios, i.e. the transition temperature and the specific heat leap, are displayed in detail for d- and p-wave pairing. The established method allows us to obtain the gap equation in a standardized form common to the models of superconductivity with an arbitrary dispersion relation. Classification of superconductors with respect to the valuation of characteristic ratios is proposed and commented on.

Equilibrium States and Thermodynamical Properties of D-Wave Paired HTSC in the Tight-Binding Model

A quasi two-dimensional d-wave paired superconductor in the BCS-type approach is considered. The tight-binding model corrections are taken into account by means of the conformal transformation defined in the framework of the formalism postulated recently by the authors. This method constitutes an extension of the van Hove scenario and exhibits a coincidence of the BCS-type and the Hubbard-type models, as well as makes possibility to determine equilibrium states of the system according to the symmetry rules. The results show essential changes in the critical temperature and specific heat jump for various forms of the dispersion relation. Additionally, a few examples of the energy gap contours obtained by the reverse conformal transformation are presented.

Application of Braid Groups in 2D Hall System Physics: Composite Fermion Structure

Introduction Elements of Hall System Physics in 2D Spaces Topological Methods of Describing Systems of Many Particles at Various Manifolds Cyclotron Braids for Multi-Particle Charged 2D Systems in a Strong Magnetic Field Recent Progress in FQHE Field Summary Comments and Supplements.

Some universal relations between the gap and thermodynamic functions plausible for various models of superconductors

It is proven that there exist some universal relations between the energy gap and the differences of the thermodynamic potential, entropy, specific heat and critical magnetic field for many two- and three-dimensional models of superconductivity with spin-singlet Cooper pairs forming \textit{s} or \textit{d} or \textit{g} etc. states. The obtained formulae make it possible to derive thermodynamic functions and, in particular, the superconducting specific heat and the critical magnetic induction in the whole temperature range

Electromagnetic response in kinetic energy driven cuprate superconductors: Linear response approach

0\leq T\leq T_{c}

ON A MODEL OF SUPERCONDUCTIVITY REALIZED IN THE METALLIC PHASE OF STRONGLY CORRELATED ELECTRONS REVEALING A FIRST-ORDER PHASE TRANSITION

employing the form of

EXPLANATION OF COMPOSITE FERMION STRUCTURE IN FRACTIONAL QUANTUM HALL SYSTEMS

\Delta(T)