Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, S. A. S. Nagar, Manauli 140306, India.
Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany.
Nat Commun. 2017 Jan 10;8:13974. doi: 10.1038/ncomms13974.
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 T=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.
一种 Weyl 半金属是一种拓扑非平庸的物质相，它承载着无质量的 Weyl 费米子，自其理论发现 80 多年以来，这些粒子一直难以捉摸。 Weyl 半金属表现出独特的输运性质和极高的表面自旋极化。在这里，我们表明通过在 TaAs 单晶上形成与银（Ag）的金属点接触，可以实现临界温度为 T=7 K 的介观超导相，而 Ag 和 TaAs 都不是超导体。这种点接触的 Andreev 反射光谱揭示了 1.2 MeV 的超导能隙，与高达 60%的高传输自旋极化共存，表明通过 TaAs 上的点接触流动着高度极化的超导电流。因此，除了发现一种新型介观超导相之外，我们的结果还表明 Weyl 半金属上的点接触在自旋电子学应用中具有潜在的重要性。
