Understanding polaronic transport in complex oxides by combining precise synthesis and first-principles many-body theory.

In complex oxides, charge carriers often couple strongly with lattice vibrations to form polaronsentangled electron-phonon quasiparticles whose transport properties remain difficult to characterize. Experimental access to intrinsic polaronic transport requires ultraclean samples, while theoretical description demands methods beyond low-order perturbation theory. Here, we show a predictive theory-experiment workflow to study polaron transport in complex oxides.Focusing on a prototypical polaronic oxide, anatase TiO 2 , we combine growth of high-quality oxygen-vacancy-doped films using hybrid molecular beam epitaxy (MBE) with a first-principles electron-phonon diagrammatic Monte Carlo (FEP-DMC) framework recently developed for accurate polaron predictions. Our films exhibit record-high electron mobility for anatase TiO 2 , in excellent agreement with FEP-DMC calculations conducted prior to experiment, which predict a room-temperature mobility of 45 ± 15 cm 2 V -1 s -1 and a mobility-temperature scaling of μ ∝ T -1.9 ± 0.077 . Microscopic analysis using scanning transmission electron microscopy and X-ray photoelectron spectroscopy reveals the role of oxygen vacancies in modulating transport at lower temperatures. FEP-DMC further provides quantitative insight into polaron formation energy, phonon cloud distribution, lattice distortion around the polaron, and the polaronic contribution to mobility. Together, these results provide a deeper microscopic understanding of large-polaron transport in a complex oxide and provide the blueprint to characterize other polaronic materials.