  We theoretically study the acoustic phonon limited mobility in n-doped
two-dimensional MoS2 for temperatures T < 100 K and high carrier densities
using the Boltzmann equation and first-principles calculations of the acoustic
electron-phonon (el-ph) interaction. In combination with a continuum elastic
model, analytic expressions and the coupling strengths for the deformation
potential and piezoelectric interactions are established. We furthermore show
that the deformation potential interaction has contributions from both normal
and umklapp processes and that the latter contribution is only weakly affected
by carrier screening. Consequently, the calculated mobilities show a transition
from a high-temperature \mu T^{-1} behavior to a stronger \mu T^{-4} behavior
in the low-temperature Bloch-Gruneisen regime characteristic of unscreened
deformation potential scattering. Intrinsic mobilities in excess of 10^5 cm^2
V^{-1} s^{-1} are predicted at T < 10 K and high carrier densities (n > 10^{11}
cm^{-2}). At 100 K, the mobility does not exceed ~7 x 10^3 cm2 V^{-1} s^{-1}.
Our findings provide new and important understanding of the acoustic el-ph
interaction and its screening by free carriers, and is of high relevance for
the understanding of acoustic phonon limited mobilities in general.
