Electron mobilities in SrTiO3 and KTaO3: Role of phonon anharmonicity, mass renormalization, and disorder

Accurately predicting carrier mobility in strongly anharmonic solids necessitates a precise characterization of lattice dynamics as a function of temperature. We achieve consistency with experimental electron mobility data for bulk KTaO3 and SrTiO3 above 150 K by refining the Boltzmann transport equations. This refinement includes incorporating temperature-dependent anharmonic phonon eigenfrequencies and eigenmodes into the electron-phonon interaction tensor, while maintaining the derivatives of the Kohn-Sham potential as computed in density functional perturbation theory. Using efficient machine-learned force fields and the stochastic self-consistent harmonic approximation, we accurately compute the dynamical matrices. At room temperature, the calculated mobility for SrTiO3 exceeds experimental values by an order of magnitude, whereas the overestimation for KTaO3 is much less pronounced. This discrepancy is explained through the more significant electron mass renormalization near the conduction-band bottom due to anharmonic electron-phonon coupling and the presence of local disorder in SrTiO3.