Semiconductor-metal transition in semiconducting bilayer sheets of transition metal dichalcogenides

TL;DR

This study demonstrates that applying vertical pressure to bilayer transition metal dichalcogenides can reversibly induce a semiconductor-to-metal transition, enabling controlled band gap tuning for various applications.

Contribution

It reveals a universal, reversible S-M transition in bilayer TMDs under pressure, supported by first-principles calculations and band gap correction methods.

Findings

Band gap decreases smoothly with pressure.

S-M transition occurs at a critical pressure.

Transition is reversible and reproducible with different computational methods.

Abstract

Using first-principles calculations we show that the band gap of bilayer sheets of semiconducting transition metal dichalcogenides (TMDs) can be reduced smoothly by applying vertical compressive pressure. These materials undergo a universal reversible semiconductor to metal (S-M) transition at a critical pressure. S-M transition is attributed to lifting the degeneracy of the bands at fermi level caused by inter-layer interactions via charge transfer from metal to chalcogens. The S-M transition can be reproduced even after incorporating the band gap corrections using hybrid functionals and GW method. The ability to tune the band gap of TMDs in a controlled fashion over a wide range of energy, opens-up possibility for its usage in a range of applications.