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The normal state resistivity in multiband superconductors has been analyzed in the framework of Eliashberg theory. The results are compared with measurements of the temperature dependence of normal state resistivity of high-purity BaKFeAs single crystals with the highest reported transition temperature T = 38.5 K. The experimental data demonstrate strong deviations from the Bloch-Grüneisen behavior, namely the tendency to saturation of the resistivity at high temperatures. The observed behavior of the resistivity is explained within the two band scenario when the first band is strongly coupled and relatively clean, while the second band is weakly coupled and is characterized by much stronger impurity scattering. [ABSTRACT FROM AUTHOR]

We developed a self-consistent method for the calculation of the density of states N(ε) in SF bilayers. It is based on the quasi-classical Usadel equations and takes into account the suppression of superconductivity in the S layer due to the proximity effect of the F metal, as well as existing mechanisms of the spin dependent electron scattering. We demonstrate that the increase of the spin orbit or spin flip electron scattering rates results in completely different transformations of N(ε) at the free F layer interface. The developed formalism has been applied for the interpretation of the available experimental data. [ABSTRACT FROM AUTHOR]

The J(φ) relation in SFIFS, SNINS, and SIS tunnel junctions is studied. A method for the analytical solution of linearized Usadel equations has been developed and applied to these structures. It is shown that the Josephson current across the structure has a sum of sin φ and sin 2φ components. Two different physical mechanisms are responsible for the sign of sin 2φ. The first one is the depairing by current, which contributes positively to the sin 2φ term, while the second one is the finite transparency of SF or SN interfaces, which provides the negative contribution. In SFIFS junctions, where the first harmonic vanishes at the 0–π transition, the calculated second harmonic fully determines the J(φ) curve. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The results of calculations of the spatially-resolved density of states (DOS) in an S(F/N) bilayer are presented (S is a superconductor, F is a metallic ferromagnet, N is a normal metal) within quasiclassical theory in the dirty limit. Analytical solutions are obtained in the case of thin F, N layers which demonstrate the peculiar features of DOS in this system. The dependences of the minigap and the DOS peak positions on the exchange energy and parameters of the layers are studied numerically. © 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

We study the Josephson junction between two d-wave superconductors, which is discussed as an implementation of a qubit. We propose an approach to calculate the decoherence time due to an intrinsic dissipative process: quantum tunneling between the two minima of the double-well potential excites nodal quasiparticles, which lead to incoherent damping of quantum oscillations. The decoherence is weakest in the mirror junction, where the contribution of nodal quasiparticles corresponds to the superohmic dissipation and becomes small at small tunnel splitting of the energy level in the double-well potential. For available experimental data, we estimate the quality factor. [ABSTRACT FROM AUTHOR]

We study the critical temperature(T)c of FSF trilayers (F is a ferromagnet, S is a singlet superconductor), where the triplet superconducting component is generated at noncollinear magnetizations of the F layers. An exact numerical method is employed to calculate(T)c as a function of the trilayer parameters, in particular, mutual orientation of magnetizations. Analytically, we consider limiting cases. Our results determine the conditions necessary for the existence of recently investigated odd triplet superconductivity in SF multilayers.(c) 2003 MAIK. [ABSTRACT FROM AUTHOR]

Various types of current–phase relation I(φ) in superconductor–ferromagnet–superconductor (SFS) point contacts and planar double-barrier junctions are studied within the quasi-classical theory in the limit of thin diffusive ferromagnetic interlayers. The physical mechanisms leading to highly nontrivial I(φ) dependence are identified by studying the spectral supercurrent density. These mechanisms are also responsible for the 0–π transition in SFS Josephson junctions. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A quantitative theory of the Josephson effect in SFIFS junctions (S denotes bulk superconductor, F is metallic ferromagnet, and I is insulating barrier) is presented in the dirty limit. A fully self-consistent numerical procedure is employed to solve the Usadel equations for arbitrary values of the F-layer thicknesses, magnetizations, and interface parameters. In the case of antiparallel ferromagnet magnetizations, the effect of critical current I[sub c] enhancement by the exchange energy H is observed, while in the case of parallel magnetizations the junction exhibits a transition to the π state. In the limit of thin F layers, we study these peculiarities of the critical current analytically and explain them qualitatively; the scenario of the 0–π transition in our case differs from those studied before. The effect of switching between 0 and π states by changing the mutual orientation of F layers is demonstrated. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Superconductor/ferromagnet bilayers are known to exhibit nontrivial dependence of the critical temperature T[sub c] on the thickness d[sub f] of the ferromagnetic layer. We develop a general method for investigation of T[sub c] as a function of the bilayer parameters. It is shown that interference of quasiparticles makes T[sub c](d[sub f][sub ]) a nonmonotonic function. The results are in good agreement with experiment. Our method also applies to multilayered structures. © 2001 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A theoretical model of a rough surface in a d-wave superconductor is studied for the general case of arbitrary strength of electron scattering by an impurity layer covering the surface. Boundary conditions for quasiclassical Eilenberger equations are derived at the interface between the impurity layer and the d-wave superconductor. The model is applied to the self-consistent calculation of the surface density of states and the critical current in d-wave Josephson junctions. [ABSTRACT FROM AUTHOR]

The anomalous proximity effect between a d-wave superconductor and a thin disordered normal layer is studied theoretically in the framework of Eilenberger equations. It is shown that disorder of the quasiparticle reflection from this thin layer leads to the formation of an s-wave component localized near the boundary. The angular and spatial structure of the pair potential near the interface is studied. [ABSTRACT FROM AUTHOR]

Presents a corrected reprint of an article concerning Josephson Junctions in a 2002 issue of the periodical 'JETP Letters.'