Signatures of van Hove singularities in the anisotropic in-plane optical conductivity of the topological semimetal Nb$_3$SiTe$_6$

TL;DR

This study combines infrared spectroscopy and DFT calculations to identify van Hove singularities in the anisotropic optical conductivity of Nb$_3$SiTe$_6$, revealing characteristic excitations linked to its topological semimetal nature.

Contribution

It provides the first combined experimental and theoretical analysis of anisotropic optical excitations and their relation to van Hove singularities in Nb$_3$SiTe$_6$.

Findings

Identification of three prominent excitations at 0.15, 0.28, and 0.41 eV.

Correlation of excitations at 0.15 and 0.28 eV with van Hove singularities.

Confirmation of anisotropic optical behavior in the in-plane conductivity.

Abstract

We present a temperature-dependent infrared spectroscopy study on the layered topological semimetal Nb$_3$SiTe$_6$ combined with density-functional theory (DFT) calculations of the electronic band structure and optical conductivity. Our results reveal an anisotropic behavior of the in-plane ($ac$-plane) optical conductivity, with three pronounced excitations located at around 0.15, 0.28, and 0.41~eV for the polarization of the incident radiation along the $c$ axis. These excitations are well reproduced in the theoretical spectra. Based on the \textit{ab initio} results, the excitations around 0.15 eV and 0.28 eV are interpreted as fingerprints of van Hove singularities in the electronic band structure and compared to the findings for other topological semimetals.