Possible pairing symmetries in SrPtAs with a local lack of inversion center

TL;DR

This paper investigates possible unconventional pairing symmetries in SrPtAs, a superconductor with local inversion symmetry breaking, highlighting the role of spin-orbit coupling and classifying potential stable states.

Contribution

It classifies pairing symmetries in SrPtAs considering local inversion symmetry breaking and proposes candidate states using a tight-binding model.

Findings

Possible unconventional pairing states like s+f-wave and chiral d+chiral p-wave.

Spin-orbit coupling influences singlet-triplet mixing despite global inversion symmetry.

Identification of stable pairing states based on symmetry analysis.

Abstract

We discuss possible pairing symmetries in the hexagonal pnictide superconductor SrPtAs. The local lack of inversion symmetry of the two distinct conducting layers in the unit cell results in a special spin-orbit coupling with a staggered structure. We classify the pairing symmetry by the global crystal point group D_3d, and suggest some candidates for the stable state using a tight-binding model with an in-plane, density-density type pairing interaction. We may have some unconventional states like s+f-wave and a mixture of chiral d-wave and chiral p-wave. The spin orbit coupling is larger than the interlayer hopping, and the mixing between spin-singlet and triplet states can be seen in spite of the fact that the system has a global inversion center.