Discovery of tip induced superconductivity in Weyl semimetal

January 25, 2017

A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, particles that remained elusive for more than 80 years since their theoretical prediction by the German mathematical physicist Hermann Weyl in 1929, but discovered experimentally only in 2015. The Weyl semimetals exhibit unique electrical transport properties and remarkably high values of spin polarization of their electrons at their surfaces. One such Weyl semimetal is the compound TaAs.  A team of scientists from the Max Planck Institute of Chemical Physics of Solids Dresden, Germany in collaboration with scientists from the Indian Institute of Science Education and Research Mohali, India, have discovered that the superconducting phase with high critical temperature of Tc ~7 K. This superconducting phase is realized by forming the 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, these results also show that point contacts on Weyl semimetals are potentially important for applications in spintronics. 


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