Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 100: Electronic Structure of Surfaces: Spectroscopy, Surface States II
O 100.9: Vortrag
Donnerstag, 23. März 2017, 18:00–18:15, WIL C307
Double photoemission of Pb in its normal state — Yuri Aliaev, Ilya Kostanovskiy, Jürgen Kirschner, and •Frank O. Schumann — Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany
We investigated double photomemission (DPE) from a polycrystalline Pb surface at room temperature. The valence consists of 6s and 6p states which
are separated by an energy gap of 3.1 eV. This allows to investigate the electron-electron interaction of states with different orbital symmetry without hybridisation. The low-lying 5d core levels can be excited with a laboratory light source. Hence, core-valence-valence Auger-Photoelectron coincidences can be detected.
The measured DPE intensity is dominated by the emission of 5d photoelectrons and the resulting Auger electron. The Auger electron line shape has mainly contributions due the 6p electrons rather than 6s electrons. From the sum energy spectra we find that the effective Coulomb interaction Ueff is to close to zero.
The DPE intensity directly from the valence band is an order of magnitude smaller than the core-assisted emission. This is consistent with the small value of Ueff.[1,2]
We discuss the experimental prospect of Cooper pair emission upon photon absorption which has been predicted theoretically.[3]
[2] F.O. Schumann et al., Phys. Rev. B 93, 235128 (2016).
[3] K.A. Kouzakov and J. Berakdar, Phys. Rev. Lett. 91, 257007 (2003).