Strain engineering is an effective route to tune electron mobilities in two-dimensional transition metal dichalcogenides, but the underlying physical mechanisms are not yet fully uncovered. In this work, we employ ab initio Boltzmann transport calculations to investigate the evolution of electron mobility in transition metal dichalcogenides $M{X}_2$ $(M=\mathrm{Mo}, \mathrm{W}, \mathrm{Zr}, \mathrm{Hf}; X=\mathrm{S}, \mathrm{Se})$ under biaxial tensile strain. The electron mobilities of hexagonal monolayer $M{X}_2$ $(M=\mathrm{Mo}, \mathrm{W})$ increase under tensile strain. We trace this enhancement to a strain-induced downward shift of the K valley in the conduction band, which enlarges the energy separation between the K and Q valleys. This shift is driven by weakened $d_{z^2}$-orbital coupling, which in turn suppresses electron-phonon scattering. This work uncovers the microscopic mechanism underlying strain-induced enhancement of electron mobility and identifies orbital coupling as a practical design route for optimizing transport properties in two-dimensional semiconductors.

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• Electrical properties
• 2-dimensional systems
• Transition metal dichalcogenides
• Boltzmann theory
• First-principles calculations