Pair breaking in multi-orbital superconductors: an application to oxide interfaces

TL;DR

This paper studies how impurity scattering affects both conventional and unconventional superconductivity in multi-orbital oxide interfaces with spin-orbit coupling, revealing different robustness depending on impurity type.

Contribution

It provides a detailed analysis of impurity effects on superconductivity in multi-orbital oxide interfaces, highlighting protection mechanisms for different pairing states.

Findings

Magnetic disorder protects unconventional superconductivity from interband scattering.

Nonmagnetic impurities conform to Anderson's theorem, protecting conventional superconductivity.

Unconventional superconductor's critical scattering rate is increased fourfold due to spin-orbit coupling.

Abstract

We investigate the impact of impurity scattering on superconductivity in an anisotropic multi-orbital model with spin-orbit coupling which describes the electron fluid at two-dimensional oxide interfaces. As the pairing mechanism is under debate, both conventional and unconventional superconducting states are analyzed. We consider magnetic and nonmagnetic spin-dependent intra- and interorbital scattering and discuss possible microscopic realizations leading to these processes. It is found that, for magnetic disorder, the unconventional superconductor is protected against interband scattering and, thus, more robust than the conventional condensate. In case of nonmagnetic impurities, the conventional superconductor is protected as expected from the Anderson theorem and the critical scattering rate of the unconventional state is enhanced by a factor of four due to the spin-orbit coupling and anisotropic masses in oxide interfaces.