Robust two-dimensional surface superconductivity and vortex lattice in the Weyl semimetal $\gamma$-PtBi$_2$

TL;DR

This study demonstrates robust surface superconductivity and the presence of quantized vortices in the Weyl semimetal $ ext{γ}$-PtBi$_2$, confirming two-dimensional phase coherence linked to Fermi arcs.

Contribution

It provides direct evidence of vortex formation and macroscopic quantum coherence in surface superconductivity of $ ext{γ}$-PtBi$_2$, a topological semimetal.

Findings

Superconductivity with T$_C$=2.9 K linked to Fermi arcs

Observation of quantized vortices

Superconductivity persists with high robustness

Abstract

The layered compound $\gamma$-PtBi$_2$ is a topological semimetal with Fermi arcs at the surface joining bulk Weyl points. Recent work has found signatures of surface superconductivity consisting of gap openings compatible with a critical temperature orders of magnitude larger than the bulk value. However, no superconducting vortices have been identified, raising questions about the robustness of the phase coherence. Here we use very low temperature Scanning Tunneling Microscopy (STM) and find robust superconductivity with T$_C=$2.9 K and H$_{C2}\approx$1.8 T linked to the Fermi arcs. We observe quantized superconducting vortices, demonstrating two-dimensional macroscopic quantum phase coherence.