Converting normal insulators into topological insulators via tuning orbital levels

TL;DR

This paper proposes a novel method to induce topological phase transitions in insulators by tuning orbital levels through doping, demonstrated with first-principles calculations on specific perovskite compounds, expanding the potential materials for topological applications.

Contribution

It introduces a new strategy of tuning orbital levels to realize topological phase transitions, demonstrated with first-principles calculations on cubic perovskite compounds.

Findings

Carbon doping induces topological phase transition in CsGeBr3 and CsSnBr3.

Orbital level tuning can cause band inversion and topological states.

This approach broadens the range of materials that can exhibit topological properties.

Abstract

Tuning the spin-orbit coupling strength via foreign element doping and/or modifying bonding strength via strain engineering are the major routes to convert normal insulators to topological insulators. We here propose an alternative strategy to realize topological phase transition by tuning the orbital level. Following this strategy, our first-principles calculations demonstrate that a topological phase transition in some cubic perovskite-type compounds CsGeBr$_3$ and CsSnBr$_3$ could be facilitated by carbon substitutional doping. Such unique topological phase transition predominantly results from the lower orbital energy of the carbon dopant, which can pull down the conduction bands and even induce band inversion. Beyond conventional approaches, our finding of tuning the orbital level may greatly expand the range of topologically nontrivial materials.