Superconducting Tunneling Spectroscopy of Spin-Orbit Coupling and Orbital Depairing in Nb :SrTiO3

We have examined the intrinsic spin-orbit coupling and orbital depairing in thin films of Nb-doped SiTiO3 by superconducting tunneling spectroscopy. The orbital depairing is geometrically suppressed in the two-dimensional limit, enabling a quantitative evaluation of the Fermi level spin-orbit scattering using Maki's theory. The response of the superconducting gap under in-plane magnetic fields demonstrates short spin-orbit scattering times tau(so) <= 1.1 ps. Analysis of the orbital depairing indicates that the heavy electron band contributes significantly to pairing. These results suggest that the intrinsic spin-orbit scattering time in SiTiO3 is comparable to those associated with Rashba effects in SiTiO3 interfacial conducting layers and can be considered significant in all forms of superconductivity in SiTiO3.