Ab initio optical and energy loss spectra of transition metal monopnictides TaAs, TaP, NbAs, and NbP

TL;DR

This paper uses density functional theory to calculate and analyze the optical and energy loss spectra of transition metal monopnictides TaAs, TaP, NbAs, and NbP, revealing their spectral features and underlying electronic transitions.

Contribution

It provides the first comprehensive theoretical optical spectra of these topological semimetals across a broad energy range, elucidating their electronic transition mechanisms.

Findings

Spectra are largely independent of anion and polarization.

Characteristic absorption features relate to electron orbital transitions.

Energy loss spectra show plasmonic and interband transition features.

Abstract

Transition metal monopnictides represent a new class of topological semimetals with low-energy excitations, namely, Weyl fermions. We report optical properties across a wide spectral energy range for TaAs, TaP, NbAs and NbP, calculated within density functional theory. Spectra are found to be somewhat independent of the anion and the light polarization. Their features are explained in terms of the upper $s$, $p$, $d$, and $f$ electrons. Characteristic absorption features are related to the frequency dependence of the Fresnel reflectivity. While the lower part of the energy loss spectra is dominated by plasmonic features, the high-energy structures are explained by interband transitions.