Orbital limiting and modulation induced by missing parity in noncentrosymmetric superconductors

Abstract

We examine the depairing field ${H}_{c2}(T)$ of noncentrosymmetric 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 noncentrosymmetric 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 noncentrosymmetric system. The present results are relevant to the $H\text{\ensuremath{-}}T$ phase diagrams of ${\text{CePt}}_{3}\text{Si}$ and the families of ${\text{Li}}_{2}{\text{Pd}}_{3\ensuremath{-}x}{\text{Pt}}_{x}\text{B}$.