Berlin 2018 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
O: Fachverband Oberflächenphysik
O 50: Poster: Nanostructures on Surfaces II
O 50.7: Poster
Tuesday, March 13, 2018, 18:15–20:30, Poster B
Coupling of structural and electronic properties in 4/3-ML Pb/Si(111) investigated by femtosecond time- and angle-resolved 2PPE — •Abdul Samad Syed, Manuel Ligges, Vesna Mikšić Trontl, Peter Kratzer, and Uwe Bovensiepen — Fakultät für Physik, Universität Duisburg-Essen, Germany
Electronic properties and atomic structure of low dimensional systems determine each other. Scattering at steps was found, e.g., for Pb/Si(557) to lead to different electron relaxation for step down and step up directions [1]. A related, problem appears for threefold symmetry of Pb/Si(111)-(√3×√3) and we report here on the unoccupied electronic structure along [1 1 2] and [11 2] investigated by femtosecond time- and angle-resolved two photon photoemission (2PPE). Three electronic features dispersing along kx ∥ [1 1 2] were identified with binding energies 3.65, 3.5, and 3.3 eV above the Fermi level. In angle-resolved measurements the observed electronic states show for opposite momenta kx>0 and kx<0, an asymmetric intensity I(kx) and the electronic structure that appears to be different. In time-resolved experiment we find a momentum dependent change in the electron relaxation time τ(kx). Polarization dependent studies reveal a different orbital character for the different states and for opposite kx. We conclude to have identified the unidirectional anisotropy in the real and imaginary part of the electron self energy originating from the threefold surface symmetry of Pb/Si(111)-(√3×√3).
This work is funded by the DFG through research unit FOR 1700.
[1] A. Samad Syed et al., Phys. Rev. B 92, 134301 (2015).