Crystalline solids have particlelike, low-energy excitations — so-called quasiparticles — that describe collective states of many electrons interacting with the atomic nuclei. In 2015, scientists predicted the existence of an exotic new quasiparticle, dubbed a type-II Weyl fermion, that breaks the Lorentz invariance of special relativity and has no direct analog in the standard model of particle physics. The primary signature of this new particle is an electronic surface state that forms an open Fermi arc connecting Weyl points with opposite chirality. Researchers in the team of Prof. Baumberger at the DQMP, University of Geneva report multiple open Fermi arcs in semimetallic MoTe2.
Using angle-resolved photoemission, they show that the inequivalent top and bottom (001) surfaces of MoTe2 host distinct Fermi arc surface states. Employing systematic electronic structure calculations, they demonstrate that some of these arcs likely arise from type-II Weyl points and are topologically nontrivial; other arcs are not related to the topological properties of the band structure.
This work published in Physical Review X reveals that MoTe2 is a strong candidate for the realization of a type-II Weyl semimetal phase. However, it also illustrates the numerous potential pitfalls to identifying type-II Weyl fermions, providing a framework for future spectroscopic studies of new topological materials.
Read the article in Physical Review X
Read the Synopsis on the Physics website