Triplet Cooper Pair Formation by Anomalous Spin Fluctuations in Non-centrosymmetric Superconductors

TL;DR

This paper develops a microscopic theory explaining how anomalous spin fluctuations in non-centrosymmetric superconductors stabilize triplet pairing, resulting in a mixed gap with stable line nodes that match experimental observations.

Contribution

It introduces a new microscopic model showing how lack of inversion symmetry leads to anomalous spin fluctuations that promote triplet pairing in certain superconductors.

Findings

Mixed singlet-triplet gap with stable line nodes

Anomalous spin fluctuations stabilize triplet pairing

Model explains features of CePt_3Si and CeTSi_3 superconductors

Abstract

A microscopic theory for the spin triplet Cooper pairing in non-centrosymmetric superconductors like CePt_3Si and CeTSi_3 (T=Rh, Ir) is presented. The lack of inversion symmetry leads to new anomalous spin fluctuations which stabilize the triplet part in addition to the singlet part originating from the centrosymmetric spin fluctuations. It is shown that both parts have similar nontrivial momentum dependence of A_1 type. Therefore the mixed singlet-triplet gap function has accidental line nodes on both Fermi surface sheets which are stable as function of temperature. This gap function explains the salient features of CePt_3Si and CeTSi_3 superconductors.