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[en] The nonstationary Josephson I1, interference I2, and quasiparticle J currents through symmmetrical and nonsymmetrical tunnel junctions involving superconductors with charge-density waves (CDW's) were calculated. In the symmetrical (s) case the voltage V dependence of the Josephson current Is1(V) has logarithmic singularities at |eV|=2Δ, Δ+D, and 2D, where D=√((Δ2+Σ2)), Δ is the superconducting order parameter, Σ is the dielectric order parameter, and e is the elementary charge. For temperatures T≠0 the jump at a bias |eV|=D-Δ emerges in Is1(V). The Is2(V) and Js(V) possess jumps and singularities at the same biases where singularities and jumps occur in Is1(V). For the nonsymmetrical (ns) junctions, which include also the ordinary superconductor, singularities and jumps appear at biases |eV|=D+ΔBCS, Δ +ΔBCS, and (for T≠0) |D-ΔBCS| and |Δ-ΔBCS|. Here ΔBCS is the superconducting order parameter of the ordinary superconductor. The quasiparticle current Jns is an asymmetrical function of the voltage V and depends on the sign of Σ. The theory describes the properties of NbSe3 and high-Tc oxides. copyright 1997 The American Physical Society
[en] Metastability of states associated with point defects in semiconductors in an interesting fundamental property turning out to be more common than erstwhile. This article highlights two important examples of metastable defects, one in the elemental semiconductor silicon and the other in the compound semiconductor Zn Se, of significant current interest for blue-emitting devices. (author)
[en] The electronic structure of zinc chalcogenide crystals doped with nontransition V elements was studied in the cluster approximation on the basis of a physically adequate method accounting for boundary conditions. It is shown that the formation of A-centers is a specific manifestation of a general tendency toward the reconstruction (relaxation) of impurity centers, which is mainly caused by the change in crystal electronic structure upon doping. Specific features of the formation of reconstructed centers with different charge states are studied for a series of impurities and crystalline matrices. 19 refs., 3 tabs
[en] CdSe micro/nanocrystals with multiform morphologies, including multi-foots rods, flower-like structures and hollow spheres, have been successfully synthesized by a facile solvothermal method in ethylene glycol (EG). These morphologies could be achieved simply by varying the cadmium source. In addition, different crystal phases of the as-obtained CdSe micro/nanocrystals have also been successfully controlled. Furthermore, the possible growth mechanism for different morphologies and crystal phases of CdSe micro/nanocrystals were also discussed.
[en] By using an As2Se3 based holey fiber (HF) with a normal flat dispersion profiles, a flattened and broadband mid-infrared super-continuum generation is analysed. The transmission of an ultra-short pulse in the HF is numerically simulated by solving the generalized nonlinear Schrödinger equation under various parameters. The simulation results show that, by launching a pulse with a width of 50 fs and a peak power of 4.25 kW at 4375 nm into the 6 mm-long HF, a flat and broadband super-continuum at 3 dB level is successfully generated. The super-continuum covers the wavelengths from 3866 to 5958 nm which is the largest flat bandwidth reported in such a short fiber.