Two- and Three-Dimensional Superconducting Phases in the Weyl Semimetal TaP at Ambient Pressure

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 type-I Weyl semi-metals 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, T c , 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 three-dimensional. For samples fabricated with FIB, we observe, in addition to the three-dimensional superconductivity, a second superconducting phase 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.

Sondheimer oscillations as a probe of non-ohmic flow in WP2 crystals

“…At low temperatures around 3 K, a drop in resistance signals a superconducting transition. As WP 2 in bulk form is not superconducting, this likely arises from an amorphous W-rich surface layer due to the FIB fabrication similar to observations made in NbAs 33 and TaP 34 . In Fig.…”

Ultrafast Sub‐100 fs All‐Optical Modulation and Efficient Third‐Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films

“…It was shown that the second‐order susceptibility of tantalum arsenide (TaAs) is two orders of magnitude larger than for high refractive index non‐centrosymmetric dielectrics, [ 18 ] an efficient nonlinear (NL) photocurrent generation was also demonstrated, [ 19 ] the near infrared glass‐coefficient was found to be the strongest so far reported [ 20 ] and efficient catalytic activity was observed for the hydrogen evolution reaction. [ 21 ] So far, experimental reports were limited to bulk [ 22,23 ] or micro structuring of the bulk crystal, [ 8,10,20 ] representing a natural restriction to the development of on‐chip applications.…”

Berezinskii-Kosterlitz-Thouless transition in the type-I Weyl semimetal PtBi$_2$

“…To our knowledge, and excluding the case of effective 2D layered superconductors 58,59 , the flake is five times thicker than any superconducting films exhibiting a BKT transition reported so far 60 , making PtBi 2 a prime candidate to study low dimensional superconductivity. Among the few Weyl semimetals showing a superconducting transition under ambiant pressure [61][62][63][64][65] , PtBi 2 is, together with MoTe 2 66 , the only one exhibiting such a 2D superconductivity.…”