Understanding topological phase transition in transition metal dichalcogenides

TL;DR

This paper reveals that the topological phase transition in transition metal dichalcogenides (TMDs) differs from conventional theories, showing varied band inversion behaviors across different TMDs, which challenges existing understanding.

Contribution

The study uncovers that TPT in TMDs occurs through different orbital band inversions than previously thought, providing new insights into their topological properties.

Findings

MS2 and MSe2 show band inversion with chalcogen p orbitals moving below metal d orbitals.

In MTe2, the band inversion occurs between metal d orbitals.

The results challenge the conventional view of TPT in TMDs.

Abstract

Despite considerable interest in layered transition metal dichalcogenides (TMDs), such as MX2 with M = (Mo, W) and X = (S, Se, Te), the physical origin of their topological nature is still poorly understood. In the conventional view of topological phase transition (TPT), the non-trivial topology of electron bands in TMDs is caused by the band inversion between metal d and chalcogen p orbital bands, where the former is pulled down below the latter. Here, we show that, in TMDs, the TPT is entirely different from the conventional speculation. In particular, MS2 and MSe2 exhibits the opposite behavior of TPT, such that the chalcogen p orbital band moves down below the metal d orbital band. More interestingly, in MTe2, the band inversion occurs between the metal d orbital bands. Our findings cast doubts on the common view of TPT and provide clear guidelines for understanding the topological nature in new topological materials to be discovered.