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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Charge carriers in complex oxides form polarons, which are entangled electron-phonon quasiparticles.
• Characterizing polaron transport is challenging due to strong electron-phonon coupling and the need for advanced theoretical methods.
• Understanding polaron behavior is crucial for designing advanced electronic materials.

Purpose of the Study:

• To establish a predictive theory-experiment workflow for studying polaron transport in complex oxides.
• To investigate polaron transport in anatase TiO2, a prototypical polaronic oxide.
• To provide a microscopic understanding of large-polaron transport and its contribution to material properties.

Main Methods:

• Growth of high-quality oxygen-vacancy-doped anatase TiO2 films using hybrid molecular beam epitaxy (MBE).
• Application of a first-principles electron-phonon diagrammatic Monte Carlo (FEP-DMC) framework for accurate polaron predictions.
• Microscopic analysis using scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS).

Main Results:

• Achieved record-high electron mobility in anatase TiO2 films, consistent with FEP-DMC predictions.
• FEP-DMC predicted 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.
• Identified the role of oxygen vacancies in modulating transport at lower temperatures and quantified polaron formation energy and lattice distortion.

Conclusions:

• The developed workflow successfully characterizes large-polaron transport in complex oxides.
• This study provides a deeper microscopic understanding of polaron formation and transport mechanisms.
• The established blueprint can be applied to characterize other polaronic materials for future electronic applications.