Surface and bulk superconductivity at ambient pressure in the Weyl semimetal TaP

TL;DR

This study reports the discovery of both surface and bulk superconductivity at ambient pressure in the Weyl semimetal TaP, with implications for topological quantum phenomena and potential quantum computing applications.

Contribution

It is the first demonstration of intrinsic superconductivity in TaP crystals at ambient pressure, including both bulk and surface phases, without the need for external pressure or surface treatments.

Findings

Superconductivity observed in as-grown TaP crystals at 1.7-5.3 K.

Bulk superconductivity exists in the as-grown crystal, despite inhomogeneity.

Surface superconductivity appears in samples processed with FIB etching.

Abstract

The motivation to search for signatures of superconductivity in Weyl semi-metals and other topological phases lies in their potential for hosting exotic phenomena such as nonzero-momentum pairing or the Majorana fermion, a viable candidate for the ultimate realization of a scalable quantum computer. Until now, however, all known reports of superconductivity in Weyl semimetals have arisen through surface contact with a sharp tip, focused ion-beam surface treatment or the application of high pressures. Here, we demonstrate the observation of superconductivity in single crystals, even an as-grown crystal, of the Weyl semi-metal tantalum phosphide (TaP), at ambient pressure. A superconducting transition temperature, $Tc$, varying between 1.7 and 5.3 K, is observed in different samples, both as-grown and microscopic samples processed with focused ion beam (FIB) etching. Our data show that the superconductivity present in the as-grown crystal is inhomogeneous yet exists in the bulk. For samples fabricated with FIB, we observe, in addition to the bulk superconductivity, a second superconducting state that resides on the sample surface. Through measurements of the characteristic fields as a function of temperature and angle, we are able to confirm the dimensionality of the two distinct superconducting phases.