Shutovskyi A. Phase coherence effects in supercond and two-band superconnducting tunnel junctions based on single-baductors

The thesis is devoted to study the influence of depairing effects and nonmagnetic impurities on the shape of a current density dependence on the phase difference in an SIS tunnel junction for the temperatures close to the critical temperature. As a result, the theoretical investigation is based on the Ginzburg-Landau that is an asymptotical form of microscopic theory of superconductivity at the temperatures close to the critical temperature. The obtained result for the nonsinusoidal current-phase relation is used with the aim to study the fluxon dynamics in pure and long Josephson junctions. The presented modified sine-Gordon equation with nosinusoidal current-phase relation is used with the aim to analyze the influence of the dielectric layer transparency on the spatial behavior of a fluxon. If the dielectric layer transparency increases, it is shown that the critical magnetic field decreases. If the temperatures are not close to the critical temperature, the equilibrium current states in the spatially inhomogeneous superconducting structures are investigated by the method of the quasiclassical equations that can be solved in the framework of the model with the piecewise constant order parameters. Such a sircumstance enabled one to obtain the following analytical results: the current-phase relation in the layered superconducting structures of an SIS′IS type that can be used with the aim to obtain a number of previous known results for the different superconducting junctions; the current phase relation in the superconducting tunnel junctions of an SIS type in the theory of two-band superconductivity. The Green’s function method in the theory of two-band superconductivity is constructed using the formulated mean field theory that is based on the derived representation for a partition function of a two-band superconductor. It was found that the obtained analytical formula for the current-phase relation can be used with the aim to study the pairing symmetries of the orsder parameters.