Topology, electric field induced Rashba effect and metal-insulator transition: A case study with bulk and nanostructured layered Zintl compound, KCdBi

Using first-principles calculations, we study the electronic structure of an unexplored Zintl compound, KCdBi. Our calculations establish KCdBi to be a rare example of a strong ${Z}_{2}$ topological semimetal. The compound is found to be cleavable with a small cleavage energy ($\ensuremath{\sim}0.2\phantom{\rule{0.16em}{0ex}}\mathrm{J}/{\mathrm{m}}^{2}$). The nanostructured KCdBi obtained by cleaving turned out to be a topological insulator, causing a semimetal to insulator transition upon dimensionality reduction. A rich phase diagram emerges upon application of an electric field to nanostructured KCdBi, which consists of topological insulating, ${Z}_{2}$ topological metallic, weak and strong Rashba phases. This compound thus offers a platform to study nontrivial properties tunable by electric field and dimensionality. Our findings are expected to stimulate experimental investigation of this interesting compound.