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

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.