Observation of the Type-II Weyl Semimetal Phase in MoTe2

TL;DR

This paper reports the direct observation and characterization of the electronic structure of MoTe2 as a type-II Weyl semimetal using ARPES, revealing unique Fermi arcs and spin textures that confirm its topological nature.

Contribution

It provides the first direct visualization of surface Fermi arcs and spin textures in MoTe2, confirming its classification as a type-II Weyl semimetal.

Findings

Observation of unique surface Fermi arcs in MoTe2

Demonstration of non-degenerate spin-texture of Fermi arcs

Confirmation of topological nature of MoTe2 as a type-II Weyl semimetal

Abstract

Topological Weyl semimetal (TWS), a new state of quantum matter, has sparked enormous research interest recently. Possessing unique Weyl fermions in the bulk and Fermi arcs on the surface, TWSs offer a rare platform for realizing many exotic physical phenomena. TWSs can be classified into type-I that respect Lorentz symmetry and type-II that do not. Here, we directly visualize the electronic structure of MoTe2, a recently proposed type-II TWS. Using angle-resolved photoemission spectroscopy (ARPES), we unravel the unique surface Fermi arcs, in good agreement with our ab-initio calculations. From spin-resolved ARPES measurements, we demonstrate the non-degenerate spin-texture of surface Fermi-arcs, thereby proving their non-trivial topological nature. Our work not only lead to new understandings of the unusual properties discovered in this family of compounds, but also allow for the further exploration of exotic properties and practical applications of type-II TWSs, as well as the interplay between superconductivity (MoTe2 was discovered to be superconducting recently) and their topological order.