Tunable Multifunctional Topological Insulators in Ternary Heusler Compounds

TL;DR

This paper predicts and demonstrates through first-principles calculations that many ternary Heusler compounds can be tuned to exhibit topological insulator states, expanding the potential materials for quantum spin Hall applications.

Contribution

The study identifies numerous Heusler compounds with tunable topological properties, providing a new class of materials for quantum spin Hall and related phenomena.

Findings

Approximately fifty Heusler compounds show band inversion similar to HgTe.

Topological states can be induced by strain or quantum well design.

Many compounds contain rare earth elements with additional interesting properties.

Abstract

Recently the Quantum Spin Hall effect (QSH) was theoretically predicted and experimentally realized in a quantum wells based on binary semiconductor HgTe[1-3]. QSH state and topological insulators are the new states of quantum matter interesting both for fundamental condensed matter physics and material science[1-11]. Many of Heusler compounds with C1b structure are ternary semiconductors which are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the band gap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by lattice parameter) and the magnitude of spin-orbit coupling (by the atomic charge). Based on the first-principle calculations we demonstrate that around fifty Heusler compounds show the band inversion similar to HgTe. The topological state in these zero-gap semiconductors can be created by applying strain or by designing an appropriate quantum well structure, similar to the case of HgTe. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare earth element Ln which can realize additional properties ranging from superconductivity (e. g. LaPtBi[12]) to magnetism (e. g. GdPtBi[13]) and heavy-fermion behavior (e. g. YbPtBi[14]). These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors.