Broadband optical conductivity of the chiral multifold semimetal PdGa

We present an optical conductivity study of the multifold semimetal PdGa, performed in a broad spectral range ($100--20 000 {\mathrm{cm}}^{\ensuremath{-}1}$; 12 meV--2.5 eV) down to $T=10$ K. The conductivity at frequencies below $4000 {\mathrm{cm}}^{\ensuremath{-}1}$ 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 $5500 {\mathrm{cm}}^{\ensuremath{-}1}$ and increases basically monotonously at frequencies above $9000 {\mathrm{cm}}^{\ensuremath{-}1}$. The band-structure-based computations reproduce these features of the interband conductivity and predict its linear-in-frequency behavior as frequency diminishes.