Order parameter in superconductors with non-degenerate bands

TL;DR

This paper analyzes the symmetry properties of the pairing function in noncentrosymmetric superconductors with spin-orbit coupling, revealing that their thermodynamic and Josephson behaviors resemble those of singlet superconductors.

Contribution

It introduces a general form of the pairing function in noncentrosymmetric superconductors, incorporating symmetry considerations and phase factors, and compares their tunneling and Josephson effects to conventional superconductors.

Findings

Pairing function expressed as chi(k) t(k), with chi(k) symmetric and t(k) phase-dependent

NSC states resemble singlet superconductors in thermodynamic and Josephson properties

The symmetry properties influence tunneling behavior between NSC and conventional superconductors

Abstract

In noncentrosymmetric metals, the spin degeneracy of the electronic bands is lifted by spin-orbit coupling. We consider general symmetry properties of the pairing function Delta(k) in noncentrosymmetric superconductors with spin-orbit coupling (NSC), including CePt3Si, UIr and Cd2Re2O7. We find that Delta(k) = chi(k) t(k), where chi(k) is an even function which transforms according to the irreducible representations of the crystallographic point group and t(k) is a model dependent phase factor. We consider tunnelling between a NSC and a conventional superconductor. It is found that, in terms of thermodynamical properties as well as the Josephson effect, the state of NSC resembles a singlet superconducting state with gap function chi(k).