Broadband optical conductivity of the chiral multifold semimetal PdGa

TL;DR

This study investigates the optical conductivity of the chiral multifold semimetal PdGa across a broad spectral range and temperatures, revealing dominant free carrier contributions at low frequencies and interband transitions at higher frequencies, with theoretical predictions aligning with experimental data.

Contribution

First comprehensive optical conductivity analysis of PdGa covering 100-20000 cm-1, combining experimental measurements with band-structure calculations to elucidate electronic properties.

Findings

Free carriers dominate below 4000 cm-1

Interband transitions peak around 5500 cm-1

Theoretical models predict linear frequency dependence at low frequencies

Abstract

We present an optical conductivity study of the multifold semimetal PdGa, performed in a broad spectral range (100 - 20000 cm-1; 12 meV - 2.5 eV) down to T = 10 K. The conductivity at frequencies below 4000 cm-1 is dominated by free carriers while at higher frequencies interband transitions provide the major contribution. The spectra do not demonstrate a significant temperature evolution: only the intraband part changes as a function of temperature with the plasma frequency remaining constant. The interband contribution to the conductivity exhibits a broad peak at around 5500 cm-1 and increases basically monotonously at frequencies above 9000 cm-1. The band-structure-based computations reproduce these features of the interband conductivity and predict its linear-in-frequency behavior as frequency diminishes.