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

TL;DR

This paper demonstrates a method to directly visualize the $d$-vector in nematic triplet superconductors using scanning tunneling microscopy, aiding in understanding their pairing symmetry and topological properties.

Contribution

It introduces a novel approach to visualize the $d$-vector in nematic triplet superconductors through specific scanning tunneling measurements at subgap energies.

Findings

The $d$-vector aligns with the leading wave-vector in quasi-particle interference patterns.

The $d$-vector aligns with the elongation of the local density-of-states near vortices.

The method provides a direct experimental probe of pairing symmetry.

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.