Visualizing the $d$-vector in a nematic triplet superconductor

Abstract

Recent experiments show strong evidences of nematic triplet superconductivity in doped Bi${}_2$Se${}_3$ and in Bi${}_2$Te${}_3$ thin film on a superconducting substrate, but with varying identifications of the direction of the $d$-vector of the triplet that is essential to the topology of the underlying superconductivity. Here we show that the $d$-vector can be directly visualized by scanning tunneling measurements: At subgap energies the $d$-vector is along the leading peak wave-vector in the quasi-particle-interference pattern for potential impurities, and counter-intuitively along the elongation of the local density-of-state profile of the vortex. The results provide a useful guide to experiments, the result of which would in turn pose a stringent constraint on the pairing symmetry.

5 pages, 5 color figures