Origin of infrared peaks in the optical conductivity of ytterbium compounds

TL;DR

This study uses first-principles calculations to explain the origin of infrared peaks in the optical conductivity spectra of various ytterbium compounds, linking them to interband transitions involving Yb 4f states affected by electron correlation.

Contribution

It demonstrates that the infrared spectral features in Yb compounds can be accurately described by band calculations incorporating a renormalization factor, highlighting the role of electron correlation.

Findings

Infrared peaks originate from interband transitions involving Yb 4f states.

Band calculations with renormalization reproduce experimental spectra.

Yb 4f states shift towards the Fermi level due to strong electron correlation.

Abstract

We have calculated optical conductivity [$\sigma(\omega)$] spectra of ytterbium compounds (YbAl$_3$, YbAl$_2$, YbCu$_2$Si$_2$, YbNi$_2$Ge$_2$, YbInCu$_4$, YbRh$_2$Si$_2$, YbIr$_2$Si$_2$, and YbB$_{12}$) based on the direct interband transition derived from first-principle band calculation and compared the results with the experimentally obtained $\sigma(\omega)$ spectra. The spectral feature of a peak in the middle-infrared region (mid-IR peak) and a shoulder structure in the far-infrared region (far-IR shoulder) in the experimental $\sigma(\omega)$ spectra can be described by the band calculation with a common renormalization factor. This result indicates that the infrared spectra of Yb compounds originate from the interband transition from the Yb $4f$ state but that the Yb $4f$ state shifts to the Fermi level with strong electron correlation.