Berlin 2012 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 77: Electronic structure I

O 77.1: Vortrag

Donnerstag, 29. März 2012, 16:00–16:15, MA 043

Electron-phonon coupling investigated by laser-photoemission spectroscopy in Pb/Si(111) — •Mathias Sandhofer, Dimitrios Papoutzis, Laurenz Rettig, Simon Freutel, Ltaief Ben Ltaief, Isabella Avigo, Manuel Ligges, and Uwe Bovensiepen — Fakultät für Physik, Universität Duisburg-Essen, 47048 Duisburg

We investigate different contributions to electron scattering rates in epitaxial Pb/Si(111) thin films by a linewidth analysis in photoemission spectroscopy, using frequency-quadrupled Ti:Sa laser pulses (6 eV). We consider contributions from electron-electron (e-e), electron-phonon (e-ph) and electron defect (e-df) scattering. For the investigated electronic quantum well states at five and seven monolayer film thickness the e-e contribution is 4 meV[1]. This simplifies the observation of the e-ph coupling through a temperature dependent linewidth analysis which is expected to yield a contribution one or two orders of magnitude higher[2]. A linear temperature-dependence of the linewidth is found for 40 K<T<120 K, indicating the increase of e-ph scattering rate due to an increase of the number of phonons. The obtained e-ph coupling constant is λ=0.7+-0.1. For higher temperatures (T>120 K) the linewidth remains constant. Supported by a lower linewidth for T=40 K after heating to 180 K, we explain this by a decrease in e-df scattering through a reduction of defects.

[1] Kirchmann et al., Nature Physics 6, 782 (2010)

[2] Hong I-Po et al., Phys Rev B 80, 081409 (2009)