Valley-engineering mobilities in 2D materials.

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 argue here how uniaxial strain can lift degeneracies and completely suppress scattering into entire valleys, dramatically improving performance. This is shown in detail for arsenene, where a 2% strain blocks scattering into 4 of the 6 valleys, and leads to a 600% increase in mobility. The mechanism is general and applies to other materials, including in particular the isostructural antimonene and blue phosphorene.