Spin current in metals and superconductors

The nonlocal spin transport in a nanostructure device consisting of ferromagnetic spin injector (F1) and spin detector (F2) electrodes connected to a normal conductor (N) or a superconductor (SC) is discussed. We explore how the spin transport in such a device depends on the nature of interface (metallic-contact or tunnel junction) and material parameters of electrodes by solving the spin-dependent transport equations, and obtain the conditions for efficient spin injection, spin accumulation, and spin current. In a device with SC, the spin transport is strongly affected by the onset of superconductivity. Nonlocal Spin Hall effect in metals and SCs are investigated. A superconducting qubit with a π junction is discussed.