Topologically Nontrivial Interband Plasmons in Type-II Weyl Semimetal MoTe$_2$

TL;DR

This study investigates the evolution of interband plasmons in MoTe$_2$, a topological Weyl semimetal, revealing how different fermionic contributions and phase transitions influence plasmon modes through experimental and theoretical analysis.

Contribution

It provides the first detailed analysis of interband plasmons in MoTe$_2$, highlighting the role of topological Weyl fermions and trivial electrons across phase transitions.

Findings

Observation of distinct plasmon modes in different phases

Plasmon modes dominated by interband correlations

Interband interactions involve Weyl and trivial fermions

Abstract

In many realistic topological materials, more than one kind of fermions contribute to the electronic bands crossing the Fermi level, leading to various novel phenomena. Here, using momentum-resolved inelastic electron scattering, we investigate the plasmons and their evolution across the phase transition in a type-II Weyl Semimetal MoTe$_2$, in which both Weyl fermions and trivial nonrelativistic fermions contribute to the Fermi surface in the Td phase. One plasmon mode in the 1T' phase at high temperature and two plasmon modes in the topological T$_d$ phase at low temperature are observed. Combining with first-priciples calculations, we show that all the plasmon modes are dominated by the interband correlations between the inverted bands of MoTe$_2$. Especially in the T$_d$ phase, since the electronic bands split due to inversion symmetry breaking and spin-orbit coupling, the plasmon modes manifest the interband correlation between the topological Weyl fermions and the trivial nonrelativistic electrons. Our work emphasizes the significance of the interplay between different kinds of carriers in plasmons of topological materials.