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O: Fachverband Oberflächenphysik
O 67: Ultrafast Electron Dynamics II
O 67.4: Vortrag
Mittwoch, 19. März 2025, 15:45–16:00, H11
Time-resolved two-photon photoemission of antiferromagnetic LaFeO3 — •Friederike Wührl, Antonia Rieche, Anne Oelschläger, Kathrin Dörr, and Wolf Widdra — MLU Halle-Wittenberg
Basic quantities as band gaps or the lifetime of electrons at the conduction band minimum are of strong interest for optoelectronic devives. In this context, strongly correlated oxides are rarely studied. One such example is NiO, which shows a remarkable short lifetime of <10 fs at the conduction band minimum, relaxing in a many-body in-gap state, which couples to the antiferromagnetic spin system [1].
We present time-resolved two-photon photoemission (2PPE) data on above band gap excitation of electrons in LaFeO3, a charge-transfer insulator with antiferromagnetic order, which exhibits weak ferromagnetism through spin canting. The band gap opens between hybridized O 2p – Fe 3d↑ and minority Fe 3d t2g ↓ states. Thin films of 9 nm LaFeO3 were prepared on SrRuO3/DyScO3 substrates using pulsed laser deposition. Low-energy electron diffraction confirmed the formation of single crystalline layers with a c(2x2) superstructure, indicative for the long-range magnetic ordering. In one-colour and two-colour UV-UV pump-probe experiments (hv=3.4 eV and 4.2 eV) we find three unoccupied states at 0.3, 1.3, 2.1 eV above EF, the middle one being resonantly pumped from Fe eg, ↑ states and exhibiting a short lifetime of 22 fs. At the conduction band minimum we observe a biexponential decay with lifetimes of 40 fs and 1.1 ps.
[1] Gillmeister et al. Nat. Commun. 11, 4095 (2020).
Keywords: 2PPE; time-resolved; LaFeO3; charge-transfer insulator