Low-energy excitations in type-II Weyl semimetal Td-MoTe2 evidenced through optical conductivity

TL;DR

This study investigates low-energy excitations in Td-MoTe2, revealing temperature-dependent optical transitions linked to spin-orbit split bands, enhancing understanding of its topological properties.

Contribution

The paper provides experimental optical spectra analysis combined with ab initio calculations to elucidate the band structure and excitations in Td-MoTe2, a topological material.

Findings

Detection of two strong low-energy interband transitions

Identification of a thermal shift in the lowest interband transition

Quantitative explanation of optical spectra features up to 400 meV

Abstract

Molybdenum ditelluride, MoTe2, is a versatile material where the topological phase can be readily tuned by manipulating the associated structural phase transition. The fine details of the band structure of MoTe2, key to understanding its topological properties, have proven difficult to disentangle experientially due to the multi-band character of the material. Through experimental optical conductivity spectra, we detect two strong low-energy interband transitions. Both are linked to excitations between spin-orbit split bands. The lowest interband transition shows a strong thermal shift, pointing to a chemical potential that dramatically decreases with temperature. With the help of ab initio calculations and a simple two-band model, we give qualitative and quantitative explanation of the main features in the temperature-dependent optical spectra up to 400 meV.