  Two-dimensional materials are emerging as a promising platform for ultrathin
channels in field-effect transistors. To this aim, novel high-mobility
semiconductors need to be found or engineered. While extrinsic mechanisms can
in general be minimized by improving fabrication processes, the suppression of
intrinsic scattering (driven e.g. by electron-phonon interactions) requires to
modify the electronic or vibrational properties of the material. Since
intervalley scattering critically affects mobilities, a powerful approach to
enhance transport performance relies on engineering the valley structure. We
show here the power of this strategy using uniaxial strain to lift degeneracies
and suppress scattering into entire valleys, dramatically improving
performance. This is shown in detail for arsenene, where a 2% strain stops
scattering into 4 of the 6 valleys, and leads to a 600% increase in mobility.
The mechanism is general and can be applied to many other materials, including
in particular the isostructural antimonene and blue phosphorene.
