Orbital-limiting and modulation induced by missing parity in non-centrosymmetric superconductors

TL;DR

This paper investigates how missing parity in non-centrosymmetric superconductors affects the upper critical field, revealing suppression of paramagnetic depairing and implications for specific material phase diagrams.

Contribution

It demonstrates that mixing singlet and triplet pairing states in non-centrosymmetric superconductors suppresses paramagnetic depairing, approaching the orbital-limited critical field.

Findings

Paramagnetic depairing is suppressed when singlet and triplet components are equally mixed.

The suppression occurs in both cubic and quasi-two-dimensional Rashba systems.

Results are relevant to phase diagrams of CePt₃Si and Li₂Pd₃₋ₓPtₓB.

Abstract

We examine the depairing field $H_{c2}(T)$ of non-centrosymmetric superconductors with a spin-orbit coupling larger than the Zeeman energy at $H_{c2}(0)$ by taking account of the mixing of spin-singlet and triplet pairing states due to the missing parity. When the singlet and triplet pairing components are mixed with an equal weight in a cubic non-centrosymmetric system, the paramagnetic depairing effect is significantly suppressed so that $H_{c2}(T)$ approaches its orbital-limited value. A similar event also occurs in a quasi two-dimensional Rashba non-centrosymmetric system. The present results are relevant to the $H$-$T$ phase diagrams of CePt$_3$Si and the families of Li$_2$Pd$_{3-x}$Pt$_x$B.