We develop a detailed microscopic analysis of electron transport in normal diffusive conductors in the presence of proximity induced superconducting correlation. We calculated the linear conductance of the system, the profile of the electric field and the densities of states. In the case of transparent metallic boundaries the temperature dependent conductance has a non-monotoneous "reentrant" structure. We argue that this behavior is due to nonequilibrium effects occuring in the normal metal in the presence of both superconducting correlations and the electric field there. Low transparent tunnel barriers suppress the nonequilibrium effects and destroy the reentrant behavior of the conductance. If the wire contains a loop, the conductance shows Aharonov-Bohm oscillations with the period Φ0 = h/2e as a function of the magnetic flux Φ inside the loop. The amplitude of these oscillations also demonstrates the reentrant behavior vanishing at T = 0 and decaying as 1/T at relatively large temperatures. The latter behavior is due to low energy correlated electrons which penetrate deep into the normal metal and "feel" the effect of the magnetic flux Φ. We point out that the density of states and thus the "strengh" of the proximity effect can be tuned by the value of the flux inside the loop. Our results are fully consistent with recent experimental findings.

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Using a scanning tunneling microscope we imaged Abrikosov vortex lattices in 2H-NbSe 2. At a reduced temperature of T/T c =0.6 we found a distinct decrease of the vortex-core radius with increasing magnetic field. Even at low fields H/H c2 << 1, the effect of vortex-vortex interactions on the spatial variation of the order parameter Delta (rho), is clearly evident. In order to interpret the experimental results the microscopic equations of the superconducting state are solved self-consistently. A good quantitative agreement is obtained without any variational free parameters.

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We have developed a model for the resistive transition in a transition edge sensor (TES) based on the model of a resistively and capacitively shunted junction, taking into account phase-slips of a superconducting system across the barriers of the tilted washing board potential. We obtained analytical expressions for the resistance of the TES, R(T, I), and its partial logarithmic derivatives αI and βI as functions of temperature and current. We have shown that all the major parameters describing the resistive state of the TES are determined by the dependence on temperature of the Josephson critical current, rather than by intrinsic properties of the S-N transition. The complex impedance of a pristine TES exhibits two-pole behaviour due to its own intrinsic reactance.