We demonstrate, both theoretically and experimentally, that thin dirty superconductor-normal metal bilayer with resistivity of normal metal ρN much smaller than normal-state resistivity of superconductor ρS has unique superconducting properties. First of all the normal layer provides the dominant contribution to the diamagnetic response of whole bilayer structure in wide temperature interval below the critical temperature due to proximity induced superconductivity. Secondly, the presence of the normal layer may increase the critical current Ic in several times (the effect is not connected with enhanced vortex pinning), provides strong temperature dependence of both Ic and effective magnetic field penetration depth even at temperatures much below the critical one and leads to the diode effect in parallel magnetic field. Besides of general interest we believe that the found results may be useful in construction of different kinds of superconducting detectors.

The suppression of superconductivity in disordered systems is a fundamental problem of condensed matter physics. Here we investigate the superconducting niobium-titanium-nitride (Nb 1−x TixN) thin films grown by atomic layer deposition (ALD) where disorder is controlled by the slight tuning of the ALD process parameters. We observe the smooth crossover from the disorderdriven superconductor-normal metal transition (often reffered to as fermionic mechanism) to the case where bosonic mechanism dominates and increasing disorder leads to formation of metal with Cooper pairing. We show that, in 'moderately' disordered films, the transition to zero-resistance state occurs in a full agreement with the conventional theories of superconducting fluctuations and Berezinskii-Kosterlitz-Thouless transition. However, the 'critically' disordered films violate this accord showing low-temperature features possibly indicating the Bose metal phase. We show that it is the interrelation between film's sheet resistance in the maximum, Rmax, of the resistive curve R✷(T ) and Rq = h/4e 2 that distinguishes between these two behaviors. We reveal the characteristic features in magnetoresistance of the 'critically' disordered films with Rmax > Rq. 2/9

We study the perspective of thin bilayer strips made of highly resistive (in the normal state) superconductor (S) and low resistive normal metal (N) as a detector of electromagnetic radiation. A small minigap in the quasiparticle spectra, induced in the N layer due to proximity induced superconductivity from the S layer and the ability of low resistive N layer to carry a larger superconducting current than the host dirty superconductor leads to steep temperature dependence of critical current of SN strip in wide temperature ranges. It results in higher sensitivity of current-biased SN strip to the electromagnetic radiation in comparison with S strip. We present experimental results on several microns wide MoN/Cu and MoN strips, which confirm this statement in the bolometric regime. We also discuss possible advantages of single photon counting by narrow SN strips.