Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 43: Clean surfaces III
O 43.8: Vortrag
Mittwoch, 28. März 2012, 12:15–12:30, MA 043
Exploring highly correlated materials via electron pair emission — •Lucie Behnke, Frank O. Schumann, Chang-Hui Li, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Metal oxides like NiO are usually termed "highly correlated", because the material properties are decisively determined by the electron-electron interaction. This makes them interesting candidates for electron pair spectroscopy which is particularly sensitive to the electron correlation. We have prepared ultrathin NiO/Ag(100) films and studied the electron pair emission upon electron impact. Compared to metallic Ni we observe an increase of the coincidence intensity by a factor 8-10 for NiO. Thickness dependent measurements prove that this enhancement is an intrinsic effect rather than due to an increased mean free path for NiO. The Neel temperature TN of NiO films is thickness dependent which allows to tune TN. We performed temperature dependent measurements for various thicknesses and observed no temperature variation of the coincidence intensity. This proves that the electron pair emission probes the local correlation rather than long-range order. We discuss the prospect of a quantitative characterization of the electron correlation via pair emission spectroscopy.