Tip induced unconventional superconductivity on Weyl semimetal TaAs

TL;DR

This paper reports the first observation of tip-induced unconventional superconductivity on Weyl semimetal TaAs, revealing potential Majorana modes and topological superconducting phases in a topological Weyl material.

Contribution

It demonstrates the induction of p-wave like superconductivity on TaAs via point contact spectroscopy, suggesting a new route to realize topological superconductors in Weyl semimetals.

Findings

Observation of conductance plateau and double dips indicating unconventional superconductivity

Detection of zero bias conductance peak suggesting Majorana zero modes

Interpretation with a mirror-symmetry protected topological superconductor

Abstract

Weyl fermion is a massless Dirac fermion with definite chirality, which has been long pursued since 1929. Though it has not been observed as a fundamental particle in nature, Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the surface. As a firstly discovered Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum space, which are topologically protected against small perturbations. Here, we report for the first time the tip induced superconductivity on TaAs crystal by point contact spectroscopy. A conductance plateau and sharp double dips are observed in the point contact spectra, indicating p-wave like unconventional superconductivity. Furthermore, the zero bias conductance peak in low temperature regime is detected, suggesting potentially the existence of Majorana zero modes. The experimentally observed tunneling spectra can be interpreted with a novel mirror-symmetry protected topological superconductor induced in TaAs, which can exhibit zero bias and double finite bias peaks, and double conductance dips in the measurements. Our work can open a broad avenue in search for new topological superconducting phases from topological Weyl materials and trigger intensive investigations for pursuing Majorana fermions.