PUB-2017-EFT

Evidence for topological type-II Weyl semimetal WTe2

​"Peng Li, Yan Wen, Xin He, Qiang Zhang, Chuan Xia, Zhi-Ming Yu, Shengyuan A. Yang, Zhiyong Zhu, Husam N. Alshareef and Xi-Xiang Zhang" Evidence for topological type-II Weyl semimetal WTe2
​NATURE COMMUNICATIONS, DOI: 10.1038/s41467-017-02237-1​
Peng Li, Yan Wen, Xin He, Qiang Zhang, Chuan Xia, Zhi-Ming Yu, Shengyuan A. Yang, Zhiyong Zhu, Husam N. Alshareef and Xi-Xiang Zhang
WTe2; type-II Weyl semimetal; nanoribbon
2017
​Recently, a type-II Weyl fermion was theoretically predicted to appear at the contact of electron and hole Fermi surface pockets. A distinguishing feature of the surfaces of type-II Weyl semimetals is the existence of topological surface states, so-called Fermi arcs. Although WTe2 was the first material suggested as a type-II Weyl semimetal, the direct observation of its tilting Weyl cone and Fermi arc has not yet been successful. Here, we show strong evidence that WTe2 is a type-II Weyl semimetal by observing two unique transport properties simultaneously in one WTe2 nanoribbon. The negative magnetoresistance induced by a chiral anomaly is quite anisotropic in WTe2 nanoribbons, which is present in b-axis ribbon, but is absent in a-axis ribbon. An extra-quantum oscillation, arising from a Weyl orbit formed by the Fermi arc and bulk Landau levels, displays a two dimensional feature and decays as the thickness increases in WTe2 nanoribbon.