Modern Physics Letters B

In this paper, we present a novel method to study the electronic density-of-states of intercalation materials. We present evidence that electrochemical quasi-steady state potential curves of a number of materials exhibit fine structure in striking agreement with the density of electronic states, as obtained from ab initio calculations. The ability to probe the electronic structure by our electrochemical technique seems, in most cases, to be restricted to disordered materials. We suggest that localization of the band states is essential, in order for the technique to give a good picture of their density. The electrochemical density of states is often smaller than the computed one due to kinetic effects, i.e. very slow relaxations of the charge carriers. Our highly sensitive electrochemical method opens new vistas for studying the electronic structure of disordered materials, that can be intercalated with an ionic species.

Higher manganese silicide (HMS, MnSi_1.7) films have been deposited on glass, silicon and thermally oxidized silicon substrates by the methods of magnetron sputtering and thermal evaporation. Mechanical and thermo-electric properties of the films have been measured. The hardness and elastic modulus of the films are 10.0~14.5 GPa and 156~228 GPa, respectively. The sign of the Seebeck coefficient at room temperature is positive for all samples. The resistivity at room temperature is between 0.53×10^-3 and 45.6×10^-3 ohm-cm. The energy band gap calculated from the resistivity data for the film deposited on thermally oxidized silicon substrate is about 0.459 eV.

The optical nonlinearity of an organic dye from a triphenylmethane group is measured using the Z-scan technique. The sample under study is found to exhibit the negative nature of nonlinearity, which is mainly due to the thermally induced refractive index change. Since this thermally induced refractive index change can lead to self-diffraction, the self-diffraction properties of the sample is studied by using thin films of a dye-sensitized gelatin. A He-Ne laser (633 nm) is used for both the Z-scan and self-diffraction studies. In the self-diffraction studies, it is also found that the different diffracted orders exhibit varying phase differences.

We have developed a theoretical model which studies the characteristics of laser-plasma interaction, the effect of plasma shielding and plasma radiation in the ablation process. The model is used to simulate 25 ns square pulsed laser irradiation on YBa₂Cu₃O₇ targets, and pulsed laser with the pulse width of 25 ns (FWHM) irradiation on Ni targets. The evolution of the plasma length and the transmitted intensity are performed. The model shows the variation of ablation depth with energy density. Moreover, we obtain the dependence of the ablation depth on the number of laser pulses. The satisfactorily good agreement between our results and experimental results confirms that plasma shielding plays a relevant role in the ablation process.

By considering a suitable confinement potential, we calculate the exchange-correlation induced band gap renormalization (BGR) in a V-grooved quantum wire as a function of the electron-hole plasma density and quantum wire width. The leading-order GW dynamical screening approximation is used in the calculation by treating the electron-electron Coulomb interaction and electron-optical phonon interaction. A numerical scheme has been proposed, and the screened Coulomb potential, density of states (profile of charge distribution) and the value of the renormalized gap energy are calculated. We will show that the carrier concentration, the screened confinement potential and the relative band gap renormalization are functions of the ratio of the well width in the x and y directions.

Ca-doped (x = 0.00, 0.07 and 0.20) epitaxial Y_1-xCa_xBa₂Cu₃O_7-δ thin films were prepared on SrTiO₃ (100) by PLD technique. The superconducting transition temperature is found to decrease with increasing Ca content. The AC-susceptibility data were used to determine the intergranular critical current density, when varying the field amplitude H_AC. The temperature dependence of critical current density was determined from the imaginary part of the complex susceptibility, χ′′(T), using Xing's relation. The results were analyzed in terms of superconductor-insulator-superconductor (SIS) and superconductor-normal-superconductor (SNS) type models.