Gap function of hexagonal pnictide superconductor SrPtAs from quasiparticle interference spectrum
The pnictide superconductor SrPtAs has a hexagonal layered structure containing inversion symmetry. It is formed by stacking two inequivalent PtAs layers separated by Sr layers. The former have no local (in-plane) inversion symmetry and, therefore, a (layer-)staggered Rashba spin orbit coupling appears which splits the three Kramers degenerate bands per layer into six quasi-2D bands. The symmetry of the superconducting state of SrPtAs is unknown. Three candidates, spin-singlet and as well as triplet states have been proposed. We predict the quasiparticle interference (QPI) spectrum for these gap functions in t-matrix Born approximation. We show that distinct differences in the pattern of characteristic QPI wave vectors appear. These results may be important to determine the gap symmetry of SrPtAs by STM-QPI method.