Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 66: Electronic Structure of Surfaces

O 66.14: Poster

Mittwoch, 18. März 2015, 18:15–21:00, Poster A

Double photoemission from surfaces: intensity relations — •Yuri Aliaev, Frank Oliver Schumann, Ilya Kostanovski, Gianluca Di Filippo, Zheng Wei, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany

The emission of an electron pair upon single photon absorption requires a finite electron-electron interaction. This makes double photoemission a particulary sensitvie tool to study the electron correlation in matter. This is supported by a recent theoretical work which predicts that the pair intensity is a direct reflection of the correlation strength.[1] In order to explore the validity of this we performed a study on a variety of materials. Among them are noble metals, transition metals and insulators. The latter include transition metal oxides like CoO and NiO which are also termed highly correlated. We find an increased pair emission rate of NiO and CoO compared to the metals which reaches factor of 10. This enhancement is photon energy depedent. It is highest at 23.7 eV and decreases monotonically as a function of the photon energies. At 60 eV the intensity levels for the oxides and metals are largely identical.

We also discovered that an increase of the coincidence intensity is accompanied by an increase in the singles count rate. This demonstrates that the pair emission is an efficient process at surfaces contributing up to 15% to the single electron emission. Our experimental results demonstrates that the correlation strength can be accessed by double photoemission.

[1] B.D. Napitu, J. Berakdar, Phys. Rev. B 81, 195108. (2010)