Anisotropy of the chiral, semiconducting phase LaRhC$_{2}$: a handedness resolved study

Abstract

Chirality in quantum materials is a topic of significant importance due to its profound effects on the electronic, magnetic, and optical properties of these systems. However, it is non-trivial to decouple the behavior of two enantiomorphs within the same material -- perhaps explaining why the influence of chirality on electrical properties has remained largely unexplored. In this work, we examine the electrical conductivity, magnetoresistance, and thermal expansion coefficient of LaRhC$_{2}$ -- a compound with a chiral crystal structure (tetragonal symmetry, space groups $\textit{P}$4$_{1}$ or $\textit{P}$4$_{3}$). The identification of a suitable monochiral domain was achieved via electron backscatter diffraction, which simultaneously determines crystallographic orientation and handedness. Both enantiomorphs are confirmed by single-crystal X-ray diffraction on monochiral specimens. The analysis of electrical resistivity was made possible through the single-domain extraction of enantiopure specimens from a polycrystalline sample using focused ion beam techniques. We establish that LaRhC$_{2}$ is a semiconductor with band gaps of approximately 20 meV and 33 meV parallel and perpendicular to the fourfold screw axis of the crystal structure, respectively -- consistent with band structure calculations. A significant anisotropy is also observed in the thermal expansion, electrical resistivity as well as angular-dependent magnetoresistance parallel and perpendicular o [001] crystallographic directions.