Spectroscopic evidence for type II Weyl semimetal state in MoTe2

TL;DR

This paper provides spectroscopic evidence that MoTe2 is a type II Weyl semimetal, revealing unique electronic states, Weyl points, and surface states that advance understanding of topological quantum materials.

Contribution

The study experimentally confirms the existence of a type II Weyl semimetal state in MoTe2, identifying Weyl points and novel surface states through ARPES and theoretical calculations.

Findings

Identification of Weyl points at electron-hole pocket contact points

Observation of Fermi arcs connecting Weyl points

Discovery of unique surface 'track states' in MoTe2

Abstract

In a type I Dirac or Weyl semimetal, the low energy states are squeezed to a single point in momentum space when the chemical potential Ef is tuned precisely to the Dirac/Weyl point. Recently, a type II Weyl semimetal was predicted to exist, where the Weyl states connect hole and electron bands, separated by an indirect gap. This leads to unusual energy states, where hole and electron pockets touch at the Weyl point. Here we present the discovery of a type II topological Weyl semimetal (TWS) state 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. Using ARPES, modeling, DFT and calculations of Berry curvature, we identify the Weyl points and demonstrate that they are connected by different sets of Fermi arcs for each of the two surface terminations. We also find new surface "track states" that form closed loops and are unique to type II Weyl semimetals. This material provides an exciting, new platform to study the properties of Weyl fermions.