Study on spin-triplet high-temperature superconducting cooper pairs

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To realize peculiar spin-triplet high-temperature superconducting states, we have investigated preparation and electrical properties of hetero-junctions with spin-singlet oxide, or nitride superconductors and magnetic materials.Infinite-layer oxide superconducting Sr0.9La0.1CuO2 can be successfully obtained in a-axis oriented thin films, which are favorable for the control of the junction interfaces owing to their long superconducting coherence length. Hetero epitaxial growth between a-axis superconducting Sr0.9La0.1CuO2 films and ferromagnetic Sr2CrReO6 or antiferromagnetic SrLaVMoO6 films was also achieved.The effect of insertion of ultra-thin magnetic layers in NbN superconducting junctions was examined. The junctions with a 1 nm-thick ferromagnetic CoFe insertion layer exhibited asymmetric Fraunhofer patterns with a minimum of Josephson supercurrent at zero field, which suggests the possibility of existence of spin-triplet cooper pairs due to magnetic inhomogeneity of junction interfaces.