Transport properties of chiral topological material epitaxial thin films: a comparative study between CoSi and CoSi₂

Chiral topological semimetals (C-TSMs) have recently emerged as a fascinating class of materials for studying exotic quantum phenomena. Their unique crystal symmetry, being both chiral and non-centrosymmetric, gives rise to unconventional topological quasiparticle states. A prime example is CoSi, known also for its "quasi-symmetry" protected topological features. In this study, we present controlled transport experiments on quasi-epitaxially grown highly textured CoSi thin films. Through precise manipulation of growth conditions, we are able to selectively produce either CoSi or its centrosymmetric sibling, epitaxial CoS$i_2$. This allows for a direct comparison between a chiral, non-centrosymmetric material and a non-chiral, centrosymmetric material, as the two comprise identical atomic species and have nearly equal atomic spin-orbit coupling strength. Our comparative transport measurements reveal how the distinct crystal symmetries lead to or suppress topological properties. Furthermore, we will discuss the possibility of inducing superconductivity in CoSi, considering that CoS$i_2$ is known to be superconducting.