Optical properties of $MgCNi_3$ in the normal state

TL;DR

This study investigates the optical properties of the superconductor MgCNi3, revealing its reflectance and conductivity spectra, and correlating these with electronic band structure calculations to understand its electronic transitions.

Contribution

The paper provides the first detailed optical spectra of MgCNi3 and links experimental data with theoretical band structure calculations, enhancing understanding of its electronic properties.

Findings

Reflectance drops gradually up to 33,000 cm$^{-1}$ with wiggles.

Optical conductivity shows Drude response and broad absorption features.

Features explained by intra- and interband transitions in Ni 3d and C 2p bands.

Abstract

We present the optical reflectance and conductivity spectra for non-oxide antiperovskite superconductor $MgCNi_{3}$ at different temperatures. The reflectance drops gradually over a large energy scale up to 33,000 cm$^{-1}$, with the presence of several wiggles. The reflectance has slight temperature dependence at low frequency but becomes temperature independent at high frequency. The optical conductivity shows a Drude response at low frequencies and four broad absorption features in the frequency range from 600 $cm^{-1}$ to 33,000 $cm^{-1}$. We illustrate that those features can be well understood from the intra- and interband transitions between different components of Ni 3d bands which are hybridized with C 2p bands. There is a good agreement between our experimental data and the first-principle band structure calculations.