Direct observation of the surface superconducting gap in the topological superconductor candidate \beta-PdBi2

TL;DR

This study directly measures the superconducting gap in ta-PdBi2, a candidate topological superconductor, revealing isotropic gaps and a small difference between surface and bulk bands, supporting its topological nature.

Contribution

It provides the first direct, high-resolution measurement of the superconducting gap in ta-PdBi2, confirming its potential as a topological superconductor.

Findings

Isotropic superconducting gaps observed in multiple bands.

Difference of about 0.1 meV between surface and bulk gaps.

Supports ta-PdBi2 as a topological superconductor.

Abstract

\beta-PdBi2 is one of the candidates for topological superconductors with a superconducting (SC) transition temperature (Tc) of 5.3 K, in which parity mixing of spin singlet and spin triplet has been anticipated, being crucial for the further understanding of relationship with inversion symmetry and parity mixing in the superconductivity. In this work, we measured the SC gap in high-quality single crystal of \beta-PdBi2 by using high-resolution laser angle-resolved photoemission spectroscopy below Tc. We found the isotropic SC gaps in momentum space for multiple bands, and observed that the difference between the SC gap of the topological surface bands and the bulk bands is about 0.1 meV, consistent with other experimental results. These direct and quantitative experimental results support the possibility of \beta-PdBi2 as a topological superconductor, characterized by unique crystal and electronic band structures.