Modern Physics Letters B

Theoretical understanding of the vortex states of type II superconductors is reviewed, with a focus on thermodynamic phases and phase transitions. Results derived from computer simulations by our group are summarized. A new phase diagram for inter-layer Josephson vortices in layered superconductors is proposed.

In this letter, we evaluate the effective velocities probability distribution associated to a classical ideal gas in thermodynamical equilibrium, but in the presence of fluctuations of the (inertial) mass parameter of the molecules. We obtain in the context of linear response theory of the mass fluctuations and the usual Boltzman framework the combined statistics of Boltzman and Tsallis as an outcome of the study for our effective Fractal gas distribution probability. This result explains from first principles the Tsallis-inverse power law distribution previously only speculated on in the literature. Finally, we give a new mathematical proof of the Boltzman ergodic theorem in classical statistics mechanics.

Using the two-time Green's function method, we analyze the temperature effect on the famous Cirac and Zoller model. Formulas for the average number of different mode phonons and the deviation of its internal state from its ground state are derived. The influence of the internal state energy and trap frequency on the number of phonons is also discussed. The upper limit of temperature for regular quantum computation in the Cirac and Zoller model is obtained.

Within the weak-coupling BCS scheme we derive a general form of the coefficients in the Ginzburg–Landau expansion of the free energy of a superconductor for the case of a Fermi level close to a Van Hove singularity (VHS). A simple expression for the influence of the VHS on the specific heat jump is then obtained for the case where gaps for different bands are distinct but nearly constant at the corresponding sheets of the Fermi surface.

Electron tunneling in small-area junctions has been treated. It is found that at the appropriate set of barrier parameters and electronic characteristics of the electrodes, the quantization of the lateral wave vector component manifests itself in the differential tunneling conductance as quite noticeable singularities. The dependance of the second derivative of the tunnel current versus the bias voltage calculated for the perfectly smooth quantized electrode should contain distinct periodic dips. It is shown that for real not perfectly smooth electrodes the resonance structure caused by the commensurate states may be observed.

CdGa₂S₄ was prepared in powder form by reacting CdS and Ga₂S₃. The powder had a tetragonal crystal structure with lattice parameters, a = 0.559 ± 0.005 nm, c = 1.008 ± 0.009 nm and c/a = 1.803. CdGa₂S₄ films deposited by thermal evaporation of the powder were noncrystalline. After annealing, the CdGa₂S₄ thin films contain crystals with the tetragonal crystal structure. The optical constants (the refractive index n, the absorption index k and the absorption coefficient α) were determined for CdGa₂S₄ thin films in the thickness range 170–452 nm. It was found that both n and k are independent of the film thickness and both are slightly different as deposited and annealed films. The refractive index shows anomalous dispersion in the spectral range 300–700 nm. The high frequency dielectric constant ε_∞ was determined for the as-deposited and after being annealed films. It was found that ε_∞ = 5.12 and 5.52 for the as-deposited and after being annealed films respectively. Graphical representations of (αhν)^r = f(hν) yield three linear parts, indicating the existence of two indirect and one direct allowed transitions. The values of , and for CdGa₂S₄ for the as-deposited and annealed films are presented.

A mathematical expression for the coefficient of optical absorption in amorphous GaAs referred to the far-infrared range is obtained by neglecting the spectrum contribution corresponding to structural disorder. In addition, our results are compared with experimental data and several aspects related to the electronic density of states are discussed.