High-field superconductivity in ultra-thin films, interfaces, and superlattices

In recent years, the manufacturing of controlled ultra-thin superconducting films has made impressive progress. Important examples are monoatomic or monomolecular layers on a substrate, superconducting layers in a superlattice, or superconducting interfaces and surfaces. These systems have in common the absence of inversion symmetry and hence the presence of Rashba-type spin-orbit interaction which can be tuned to some extent. We discuss the superconducting properties of ultra-thin superconducting films with Rashba spin-orbit interaction in the presence of a parallel magnetic field. Thereby we cover the range from small to large spin-orbit interactions compared with the gap parameter. We find abrupt changes in the superconducting state at a critical value spin-orbit energy ${\lambda }_c$. We speculate that this might give rise to new phenomena.