Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
O: Fachverband Oberflächenphysik
O 16: Ultrafast Electron Dynamics at Surface and Interfaces II
O 16.2: Vortrag
Montag, 27. März 2023, 15:15–15:30, TRE Phy
Transient Absorption Spectroscopy of NiO — •Mahendra Kabbinahithlu1, Tobias Lojewski1, Sergey Kovalenko2, Heiko Wende1, Uwe Bovensiepen1, Julia Stähler2, and Andrea Eschenlohr1 — 1Universität Duisburg-Essen, Fakultät für Physik und Center for Nanointegration (CENIDE), Lotharstraße 1, 47057 Duisburg, Germany — 2Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany
In nickel oxide (NiO), a correlated transition-metal oxide, the strong electron-electron repulsion splits the d-bands into an occupied lower Hubbard band (LHB) and an unoccupied upper Hubbard band (UHB). The presence of additional oxygen p-bands at the adjacent sites and their interaction with the Hubbard bands leads to complex properties governed by the Hubbard potential (U) and the charge transfer (p ↔ LHB) gap Δ. NiO is a charge-transfer insulator with the p-bands located between the LHB and the UHB (Δ < U). We present excited state dynamics in NiO thin films via time-resolved optical spectroscopy. NiO is pumped above the band gap with 4.8 eV photons and the transient absorption spectrum is probed using a time-delayed supercontinuum. The time-resolved absorption spectrum, shows within the first 500 fs positive pump-induced changes at 2.2 eV and 3.2 eV which are separated from substrate contributions. We also see a strong negative change around 4.3 eV. The positive changes from in-gap states decay on a time scale of 100 fs, while the negative change represents the bleached ground state which recovers within 6 ps, potentially by interaction with phonons.