Broadband Infrared Study of Pressure-Tunable Fano Resonance and Metallization Transition in 2H-MoTe2

TL;DR

This study investigates how high pressure affects the electronic and vibrational properties of 2H-MoTe2, revealing a pressure-induced metallization not linked to band gap closure and highlighting the role of doping in Fano resonance behavior.

Contribution

It provides the first analysis of Fano line-shape in a transition metal dichalcogenide and clarifies the pressure conditions for metallization and phonon symmetrization in 2H-MoTe2.

Findings

Metallization occurs at 13-15 GPa without indirect band gap closure.

Doping levels influence Fano resonance and phonon symmetrization.

Phonon profile becomes symmetric during metallization.

Abstract

High pressure is a proven effective tool for modulating inter-layer interactions in semiconducting transition metal dichalcogenides, which leads to significant band structure changes. Here, we present an extended infrared study of the pressure-induced semiconductor-to-metal transition in 2H-MoTe2, which reveals that the metallization process at 13-15 GPa is not associated with the indirect band gap closure, occuring at 24 GPa. A coherent picture is drawn where n-type doping levels just below the conduction band minimum play a crucial role in the early metallization transition. Doping levels are also responsible for the asymmetric Fano line-shape of the E1u infrared-active mode, which has been here detected and analyzed for the first time in a Transition Metal Dichalcogenide compound. The pressure evolution of the phonon profile under pressure shows a symmetrization in the 13-15 GPa pressure range, which occurs simultaneously with the metallization and confirms the scenario proposed for the high pressure behaviour of 2H-MoTe2.