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

Gated molybdenum disulfide (⁠$MoS2$⁠) exhibits a rich phase diagram upon increasing electron doping, including a superconducting phase, a polaronic reconstruction of the band structure, 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 into the behavior of such a complex system. In this paper, we combine the solution of the Boltzmann transport equation (based on ab initio density-functional theory calculations of the electronic band structure) 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 identify 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.