Superconducting properties of noncentrosymmetric Nb_0.18Re_0.82 thin films probed by transport and tunneling experiments

Superconducting thin films of the noncentrosymmetric superconductor Nb0.18Re0.82 were successfully deposited by UHV sputtering technique. X-ray diffraction analysis indicated that the films are polycrystalline, with a preferential (nn0) orientation and the lattice parameter in agreement with the expected single α-Mn cubic phase. A detailed electrical characterization of the samples as a function of the thickness (3.5 nm < d < 142 nm) was performed both in the normal and in the superconducting states, revealing a well-established superconducting ordering, as well as an estimated value of the upper critical field, μ0Hc2, comparable with the Pauli limit. Finally, the symmetry of the order parameter was probed by tunneling spectroscopy on Al/Al2O3/Nb0.18Re0.82 heterostructures, which provides evidence for a single s-wave superconducting gap