Mesoscopic superconductivity and high spin polarization coexisting at metallic point contacts on Weyl semimetal TaAs

Leena Aggarwal,Chandra Shekhar,Vicky Süß,Ritesh Kumar,Shekhar Das,Claudia Felser,Sirshendu Gayen,Goutam Sheet

doi:10.1038/ncomms13974

Abstract

A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, the particles that remained elusive for more than 80 years since their theoretical discovery. The Weyl semimetals exhibit unique transport properties and remarkably high surface spin polarization. Here we show that a mesoscopic superconducting phase with critical temperature Tc=7 K can be realized by forming metallic point contacts with silver (Ag) on single crystals of TaAs, while neither Ag nor TaAs are superconductors. Andreev reflection spectroscopy of such point contacts reveals a superconducting gap of 1.2 meV that coexists with a high transport spin polarization of 60% indicating a highly spin-polarized supercurrent flowing through the point contacts on TaAs. Therefore, apart from the discovery of a novel mesoscopic superconducting phase, our results also show that the point contacts on Weyl semimetals are potentially important for applications in spintronics.

Highlights

A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, the particles that remained elusive for more than 80 years since their theoretical discovery
For the first time, we show the emergence of a unique superconducting phase coexisting with the highly spinpolarized surface states at mesoscopic point contacts between elemental normal metals and high quality single crystals of the Weyl semimetal TaAs
The point contact spectra presented above hint to the possible existence of a tip-induced superconducting (TISC) phase on TaAs—similar to what was observed on the 3D Dirac semimetal Cd3As2 and the topological crystalline insulator Pb0.6Sn0.4Te

Summary

Introduction

A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, the particles that remained elusive for more than 80 years since their theoretical discovery. The Weyl semimetals are topologically non-trivial and are known to exhibit exotic quantum phenomena and unique surface states[14]. It was shown that the Fermi arcs in the Weyl semimetal TaAs are highly spin-polarized which lie in a completely 2D plane on the surface of the crystal[17]. For the first time, we show the emergence of a unique superconducting phase coexisting with the highly spinpolarized surface states at mesoscopic point contacts between elemental normal metals and high quality single crystals of the Weyl semimetal TaAs. The critical temperature (Tc) of such superconducting point contacts was found to be 7 K

Methods

Results

Conclusion