Ultrafast electron dynamics upon above band-gap excitation in epitaxial LaFeO3(001) thin films

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Strong electron correlations in perovskite oxides give rise to rich and often unexpected electronic phenomena. In this study, we present a comprehensive surface-science investigation of epitaxial thin films of the chargetransfer insulator LaFeO3(001). The characterization includes low-energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), and photoemission spectroscopy. We map both the occupied and unoccupied electronic states using two-photon photoemission (2PPE) spectroscopy. Furthermore, we probe electron dynamics through an ultravioletultraviolet (UV-UV) pump-probe experiment, exciting electrons from hybridized O 2p/Fe 3d states to Fe minority-spin states above the band gap. Our results reveal three distinct unoccupied states, which we assign to Fe t 2g↓ , Fe e g↓ , and La 5d orbitals. Notably, the conduction band minimum exhibits a biexponential decay with time constants of 39 fs and 1100 fs, suggesting the presence of two independent decay pathways.