Dynamic Competition between Hubbard and Superexchange Interactions Selectively Localizes Electrons and Holes through...

Area of Science:

• Solid State Physics
• Materials Science
• Quantum Materials

Background:

• Controlling photoexcited polarons in transition metal oxides is crucial for renewable energy and quantum phase engineering.
• Previous studies indicate strong electron and spin correlations modulate polaron formation, but the interplay in polar materials requires further investigation.

Purpose of the Study:

• To investigate the interplay between strong spin and electronic correlations in gadolinium iron oxide (GdFeO3) concerning photoexcited polaron formation.
• To selectively excite ligand-to-metal charge transfer (LMCT) and metal-to-metal charge transfer (MMCT) transitions to understand their impact on polaron dynamics.

Main Methods:

• Utilized excitation-wavelength-dependent transient extreme ultraviolet (XUV) spectroscopy to probe charge transfer dynamics.
• Employed ab initio theory to model polaron localization on iron centers.
• Investigated the Fe-O-Fe superexchange interaction's role in selective polaron formation.

Main Results:

• Observed that LMCT transitions suppress photoexcited polaron formation due to a balance between superexchange and Hubbard interactions.
• Demonstrated that MMCT transitions lead to photoexcited polaron formation within 250 ± 40 fs.
• Confirmed through theory that electron and hole polarons localize on iron centers after MMCT.

Conclusions:

• Established that strong electronic and spin correlations can control strong electron-phonon coupling in polar materials.
• Achieved the first separate measurement of electron and hole polaron interactions on neighboring metal centers.
• Provided insights into charge-transfer and Mott-Hubbard insulators.