Proximity-induced superconductivity and finite energy pairing in the Rashba surface state of gold

The interplay of superconductivity and strong spin-orbit coupling has gained a lot of attention in recent year. For instance, it was realized that Cooper pairing can occur intrinsically away from the Fermi surface in j=3/2 superconductors with strong spin-orbit coupling [Phys. Rev. Research 4, L012017 (2022)]. In this work, we present a theoretical study of the proximity-induced superconducting coupling in a Rashba surface state due to its contact to an s-wave superconductor.

We combine theoretical modelling and ab initio Bogolibov-de Gennes simulations [PRB 105, 125143 (2022)] using the JuKKR density functional theory code [https://jukkr.fz-juelich.de]. We investigate the proximity effect in the Rashba surface state at the interface between Al(111) and Au(111) that arises from the combination of strong spin-orbit coupling in Au and broken symmetry at the interface. We discuss how inter-orbital pairing can occur at finite energies away from the Fermi level under an external magnetic field and comment on the pairing symmetry in the proximity-induced coupling of the Rashba surface state.