Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 87: Methods: Other (experimental)

O 87.2: Talk

Friday, March 26, 2010, 11:30–11:45, H42

Double Photoemission from Pb(111) — •Robert Wallauer¹, Stefan Voss¹, Till Jahnke¹, Achim Czasch¹, Lothar Schmidt¹, Nadine Neumann¹, Jasmin Titze¹, Hung-Keun Kim¹, Götz Berner², Michael Sing², Ralph Cleassen², Juan Carlos Campuzano³, Horst Schmidt-Böcking¹, and Reinhard Dörner¹ — ¹IKF, Universität Frankfurt — ²EP4, Universität Würzburg — ³University of Illinois at Chicago

We investigate the angular resolved single photoemission (ARPES) and double photoemission (DPE) from a Pb(111) crystal in the normal and superconducting state using a momentum resolved coincidence detection method(often referred to as COLTRIMS)[1]. The experiment was performed at the synchrotron in Berlin (BESSY-II) in single bunch operation mode at photon energies around 20 to 25eV.

Theory [2] predicts that Cooper-pairs can be observed using coincidence photoemission. We suspect that our energy resolution (around 500 meV) prevents us from observing the pairs, since the calculation predicts differences (between the normal and SC states) only in an energy range of a few meV. For photon energies above 25eV the DPE current is dominated by Auger-processes involving the 5d(5/2) and 5d(3/2) core levels emitting Auger-electrons with a angular dependence on the emission direction of the Photoelectron which is not understood so far.

[1] M.Hattass et. al, Rev. Sci. Instr., 75, 2373 (2004) [2] K. A. Kouzakov and J. Berakdar Phys. Rev. Lett., 91, 257007 (2003)