Inter-orbital Cooper pairing at finite energies in Rashba surface states

TL;DR

This paper investigates how Rashba surface states in Au/Al heterostructures exhibit finite-energy inter-orbital superconducting pairing, combining DFT and effective models to reveal mixed singlet-triplet pairing characteristics.

Contribution

It introduces a combined DFT and low-energy model approach to predict and analyze finite-energy inter-orbital superconducting pairing in Rashba surface states.

Findings

Finite-energy superconducting pairing predicted in Au/Al heterostructures.

Inter-orbital pairing exhibits mixed singlet-triplet character.

Methodology provides general recipes for exploring inter-orbital pairing away from Fermi energy.

Abstract

Multi-band effects in hybrid structures provide a rich playground for unconventional superconductivity. We combine two complementary approaches based on density-functional theory (DFT) and effective low-energy model theory in order to investigate the proximity effect in a Rashba surface state in contact to an $s$-wave superconductor. We discuss these synergistic approaches and combine the effective model and DFT analysis at the example of a Au/Al heterostructure. This allows us to predict finite-energy superconducting pairing due to the interplay of the Rashba surface state of Au, and hybridization with the electronic structure of superconducting Al. We investigate the nature of the induced superconducting pairing and quantify its mixed singlet-triplet character. Our findings demonstrate general recipes to explore real material systems that exhibit inter-orbital pairing away from the Fermi energy.