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Coexisting Large and Small Polarons in Photoexcited CeO2

Valentina Mazzotti, Eleonora Spurio, Nicolas Delnour, Michael Hilke, Kirk H. Bevan, Alexander Shluger, Paola Luches, David G. Cooke

cond-mat.mtrl-sciarXiv:2608.30164

Abstract

Time-resolved terahertz (THz) spectroscopy is used to probe polaron formation in CeO2. The ultrafast THz photoconductivity is dominated by contributions from large hole and small electron polarons. Delocalized large hole polarons are formed on a 820 50 fs time scale and are of Fröhlich type, with optical conductivity well described by a simple Drude model and a transient hole mobility of 100 cm2/Vs. Small electron polarons form via localized coupling to Ce lattice sites, revealed by reduction in the lattice Born effective charge causing a transient phonon softening. These results establish the dual polaron nature of CeO2 and provide a basis for understanding charge transfer dynamics in metal oxide photocatalysts.

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