Coherent and Dynamic Small Polaron Delocalization in CuFeO2

Journal Article · Fri Jan 02 00:00:00 EST 2026 · The Journal of Physical Chemistry Letters

DOI:https://doi.org/10.1021/acs.jpclett.5c03430· OSTI ID:3029519

Mendes, JocelynL; Bhattacharyya, Srijan; Huang, Chengye; Michelsen, Jonathan M; Klein, Isabel M; Babbe, Finn; Sayer, Thomas; Li, Tianchu; Cooper, Jason K; Liu, Hanzhe; Ginsberg, Naomi S; Montoya-Castillo, Andrés; Cushing, Scott K

Small polarons remain a bottleneck in realizing efficient transition metal oxide devices. Routes to engineer small polaron coupling to electronic states and lattice modes to control carrier localization remain unclear. Here, we measure small polaron formation in CuFeO2 using transient extreme ultraviolet reflection spectroscopy and compare to theoretical predictions in realistically parametrized Holstein models, demonstrating that polaron localization depends on coupling to high-frequency versus low-frequency phonon bath components. We measure small polaron formation on a comparable ∼100 fs timescale to other Fe(III) compounds. Dynamic delocalization of the polaron follows formation through a coherent lattice expansion between Fe-O layers and charge-sharing with surrounding Fe(IV) states. Simulations reveal two major factors dictate polaron formation timescales: phonon density and reorganization energy distributions between acoustic and optical modes, matching experimental findings. Our work shows how electronic-structural coupling in a polaron-host material can be leveraged to suppress polaronic effects for various applications.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: US Department of Energy; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Chemical Sciences, Geosciences & Biosciences Division (SC-22.1)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 3029519
• Journal Information: The Journal of Physical Chemistry Letters, Journal Name: The Journal of Physical Chemistry Letters Journal Issue: 2 Vol. 17
• Country of Publication: United States
• Language: English