Electronic origin of stability of 2D 1H-phase Janus transition metal dichalcogenides and beyond

TL;DR

This paper investigates the electronic factors influencing the stability of 2D Janus transition metal dichalcogenides, identifying key electronic interactions that determine stability and proposing strategies to synthesize new stable ferromagnetic Janus materials.

Contribution

It reveals the electronic origin of stability in 2D Janus TMDs and introduces an electron compensation strategy to stabilize new Janus systems.

Findings

Group-VIB monolayers are more stable and have been experimentally synthesized.

Electronic interactions near the Fermi level determine stability.

Predicted stable ferromagnetic Janus transition metal halides.

Abstract

Janus transition metal dichalcogenides (JTMDs) monolayers have emerged as a new paradigm to broaden the family of two-dimensional (2D) materials. Despite numerous theoretical predictions of JTMDs, their experimental realization remains scarce, most probably due to intrinsic structural fragility. We identify a dependence of the structural stability of 1H-phase JTMDs on the transition metal group, with Group-VIB-based monolayers exhibiting robust stability, as evidenced by the successful synthesized MoSSe and WSSe. The group-dependent stability arises from the competition between metal-ligand ionic bonding and ligand-ligand covalent bonding, as well as the high-energy d-electron orbital splitting. We propose an electron configuration that describes the interactions of electrons near the Fermi level to correlate the stability, and introduce an electron compensation strategy to stabilize certain unstable JTMDs systems. Guided by the electronic origin of stability, we predict a family of stable 2D Janus transition metal halides with intrinsic ferromagnetic valley properties. This work bridges the gap between electronic structure and stability predictions, and extends the design rules for synthesizing 2D Janus materials.