# Optical Response of Chiral Multifold Semimetal PdGa

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Results and Discussion

`optic`module [52]. Figure 3 shows the density of states (DOS) of PdGa, as well as the atomic densities of Pd and Ga separately. It can be clearly seen that the majority of carriers at the Fermi surface, as well as electrons involved in optical transitions far beyond the visible spectrum, are entirely contributed by Pd. Significant contributions to the DOS from Ga arise at energies only as low as $-15\phantom{\rule{3.33333pt}{0ex}}\mathrm{eV}$, and beyond.

## 3. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**(

**a**) The crystal structure of PdGa. The Pd and Ga atoms are arranged chirally along the c-axis, with a distinct handedness, giving rise to chiral properties in the band structure and optical interactions. (

**b**) Fermi surface of PdGa. (

**c**) Brillouin zone of PdGa representing the high symmetry points used in the band structure plots. (

**d**) Contributions of the different bands to the Fermi surface, sorted from lowest to highest energy going from left to right.

**Figure 2.**Band structure of PdGa (

**a**) with spin-orbit coupling (SOC). Bands that cross the Fermi surface are labeled in pairs ${A}_{\pm}$ to ${D}_{\pm}$, with respect to their energy. The Fermi energy is positioned at ${E}_{F}=0$ eV. The label ± refer to spin pairs, which split away from high symmetry points. This splitting, due to lack of inversion and mirror symmetries, gives rise to a 4-fold intersection at $\Gamma $ and 6-fold intersection at R, both with Chern numbers of magnitude $\left|\chi \right|=4$. (

**b**) Magnified view of the band structure around the $\Gamma $-point without SOC. (

**c**) Magnified view around $\Gamma $ with SOC.

**Figure 3.**Density of states of PdGa and the atoms Pd and Ga separately. The Gd contribution is negligible, and has been magnified by a factor of 10. Most bands around the Fermi energy are thus contributed by the Pd atoms, underlining the relevance of chirality among carriers and optical transition. The Fermi level is positioned at ${E}_{F}=0$ eV as indicated by the blue dotted line.

**Figure 4.**(

**a**) The calculated real part of the interband optical conductivity ${\sigma}_{1}\left(\omega \right)$ with weight analysis. The features were sorted according to the labelling in Figure 2a. (

**b**) Intra-, interband, and total optical conductivity ${\sigma}_{1}\left(\omega \right)$ of PdGa for parameters $\Gamma =2.5\phantom{\rule{3.33333pt}{0ex}}\mathrm{meV}$ and ${\omega}_{p}=4.43\phantom{\rule{3.33333pt}{0ex}}\mathrm{eV}$.

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Polatkan, S.; Uykur, E.
Optical Response of Chiral Multifold Semimetal PdGa. *Crystals* **2021**, *11*, 80.
https://doi.org/10.3390/cryst11020080

**AMA Style**

Polatkan S, Uykur E.
Optical Response of Chiral Multifold Semimetal PdGa. *Crystals*. 2021; 11(2):80.
https://doi.org/10.3390/cryst11020080

**Chicago/Turabian Style**

Polatkan, Sascha, and Ece Uykur.
2021. "Optical Response of Chiral Multifold Semimetal PdGa" *Crystals* 11, no. 2: 80.
https://doi.org/10.3390/cryst11020080