Lunan Huang

TL;DR: In this article, the Weyl semimetal state in an inversion-symmetry-breaking single-crystalline solid, Niobium arsenide (NbAs), has been discovered.

TL;DR: This work identifies the Weyl points and demonstrates that they are connected by different sets of Fermi arcs for each of the two surface terminations and finds new surface 'track states' that form closed loops and are unique to type II Weyl semimetals.

TL;DR: In this article, a type II topological Weyl semimetal (TWS) was discovered in pure MoTe2, where two sets of WPs (W2+-, W3+-) exist at the touching points of electron and hole pockets and are located at different binding energies above Ef.

Abstract: In recently predicted type-II Weyl semimetals, the Weyl states connect hole and electron bands that would otherwise be separated by an indirect gap. The set of points in the momentum space at which both bands touch are called Weyl points and are connected by Fermi arcs at the surface of the sample. Experimental evidence confirmed existence of these exotic fermions in MoTe${}_{2}$ and Mo${}_{x}$W${}_{1-x}$Te${}_{2}$. Here, the authors show that such states also exist in pure WTe${}_{2}$ and are very sensitive to strain. While flat undistorted portions of the sample show well defined Fermi arcs -- a clear signature of Weyl fermions -- strain due to bulking of the surface in other locations suppresses this state and destroys the Weyl state. Such high sensitivity to strain provides a simple way to tune properties of Weyl Fermions and explore the physics of these unusual objects.