Strong band-filling-dependence of the scattering lifetime in gated MoS2 nanolayers induced by the opening of intervalley scattering channels

TL;DR

This study combines theoretical calculations and experimental data to analyze how electron doping affects charge-carrier scattering in gated MoS2, revealing doping-induced intervalley scattering channels that significantly reduce the scattering lifetime.

Contribution

It provides a detailed analysis of the doping-dependent scattering lifetime in MoS2, highlighting the role of intervalley scattering channels opened by Lifshitz transitions.

Findings

Scattering lifetime is strongly suppressed at specific doping levels.

Intervalley scattering channels between K/K' and Q/Q' valleys are responsible.

Lifshitz transitions induce new scattering pathways affecting charge transport.

Abstract

Gated molybdenum disulphide (MoS2) exhibits a rich phase diagram upon increasing electron doping, including a superconducting phase, a polaronic reconstruction of the bandstructure, and structural transitions away from the 2H polytype. The average time between two charge-carrier scattering events - the scattering lifetime - is a key parameter to describe charge transport and obtain physical insight in the behavior of such a complex system. In this work, we combine the solution of the Boltzmann transport equation (based on ab-initio density functional theory calculations of the electronic bandstructure) with the experimental results concerning the charge-carrier mobility, in order to determine the scattering lifetime in gated MoS2 nanolayers as a function of electron doping and temperature. From these dependencies, we assess the major sources of charge-carrier scattering upon increasing band filling, and discover two narrow ranges of electron doping where the scattering lifetime is strongly suppressed. We indentify the opening of additional intervalley scattering channels connecting the simultaneously-filled K/K' and Q/Q' valleys in the Brillouin zone as the source of these reductions, which are triggered by the two Lifshitz transitions induced by the filling of the high-energy Q/Q' valleys upon increasing electron doping.