Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 24: Correlated Electrons: (General) Theory 2
TT 24.9: Vortrag
Mittwoch, 25. März 2009, 12:00–12:15, HSZ 301
Band formation vs. local correlations: NiO — •T. Haupricht1, R. Gierth1, J. Weinen1, S. G. Altendorf1, A. Hendricks1, Y.-Y. Chin1,2, Z. Hu1, J. Gegner1, H. Fujiwara1, D. Regesch1, H. H. Hsieh3, H.-J. Lin2, C. T. Chen2, and L. H. Tjeng1 — 1Institute of Physics II, University of Cologne, Germany — 2National Synchrotron Radiation Research Center, Hsinchu, Taiwan — 3Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan
Modeling the electronic structure of NiO is a true theoretical challenge. Even though the general agreement between the experimental valence-band photoemission (PES) spectrum of NiO and the results of a single-site cluster configuration interaction calculation is very good, some structures in the spectrum remain unexplained. These short-comings have been recognized already when looking at the Ni 2p core level spectra, and were attributed to so-called non local screening effects involving neighboring Ni clusters [v. Veenendaal et al., PRL 70 (1993)]. We therefore set out to measure the valence band PES of NiO impurities in MgO thin films. Comparing the NiO impurity valence band spectrum to that of bulk NiO we find that there are indeed remarkable differences. On the other hand we find that the correspondence of the experimental NiO impurity valence band and the result of the cluster calculation is very good. We also compare our experimental data to the results of recent LDA+DMFT calculations [Kuneš at al., PRL 99 (2007); Kuneš at al., PRB 75 (2007); Taguchi et al., PRL 100 (2008)] with reasonable results but also showing characteristic discrepancies.