Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 73: Electronic Structure of Surfaces 1
O 73.10: Vortrag
Donnerstag, 8. September 2022, 17:15–17:30, S053
Electron correlation in SrTiO3 studied by double photoemission spectroscopy with a MHz high-order harmonics laser source — •Robin Kamrla1, Cheng-Tien Chiang1,2, Frank Oliver Schumann3, and Wolf Widdra1 — 1Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany — 2Academica Sinica, Institute of Atomic and Molecular Sciences, Taiwan — 3Max Planck Institute of Microstructure Physics, Halle (Saale), Germany
Photoelectron spectroscopy (PES) has provided deep insights into the electronic structure of solids. However, correlation effects can only be addressed indirectly. To observe such phenomena directly, double photoemission (DPE) spectroscopy is able to detect pairs of correlated photoelectrons that are emitted upon absorption of a single photon. Upon surface near doping, SrTiO3 (001) with a bandgap of 3.4 eV forms a two-dimensional electron gas (2DEG). In this contribution we present PES and DPE data for SrTiO3 (001) with and without 2DEG states at the surface, obtained by a high-order harmonic (HHG) light source at 25.2 and 30.0 eV. PES reveals a change in spectral weight of the O2p states and a surface band bending of 250 meV upon flipping SrTiO3 (001) into the 2DEG state and oxygen vacancy derived states emerging within the bandgap. In DPE, a band-bending induced shift of 500 meV, changes in the intensity of the O2p derived two hole states as well as emission from vacancy-valence pairs are identified via the two-electron sum energy spectrum. In addition, the role of Auger decays for the shallow Sr4p and O2s core level will be discussed.