# Observation of topological nodal-line semimetal in YbMnSb2 through optical spectroscopy

## TL;DR

This study identifies YbMnSb2 as a Dirac nodal-line semimetal by combining optical spectroscopy measurements with first-principles calculations, revealing a unique optical conductivity feature linked to its topological electronic structure.

## Contribution

The paper provides experimental evidence and theoretical analysis confirming YbMnSb2 as a topological nodal-line semimetal, highlighting the origin of its optical conductivity features.

## Key findings

- Observation of a flat optical conductivity region at 300cm-1
- Identification of a frequency-independent optical component
- Confirmation of Dirac nodal line near Fermi level

## Abstract

The optical properties of YbMnSb2 have been measured in a broad frequency range from room temperature down to 7 K. With decreasing temperature, a flat region develops in the optical conductivity spectra at about 300cm-1, which can not be described by the well-known Drude-Lorentz model. A frequency-independent component has to be introduced to model the measured optical conductivity. Our first-principles calculations show that YbMnSb2 possesses a Dirac nodal line near the Fermi level. A comparison between the measured optical properties and calculated electronic band structures suggests that the frequency-independent optical conductivity component arises from interband transitions near the Dirac nodal line, thus demonstrating that YbMnSb2 is a Dirac nodal line semimetal.