Graduate School of Frontier Biosciences, Osaka University

Japanese

An investigation of electron-phonon coupling via phonon dispersion measurements in graphite using angle-resolved photoelectron spectroscopy

Journal Sci. Rep. (2013) online
Authors Shin-ichiro Tanaka (1), Masaharu Matsunami (2, 3), Shin-ichi Kimura (2, 3, 4)
  1. The Institute of Industrial and Scientific Research, Osaka University, 567-0047 Mihogaoka, Ibaraki, Osaka, Japan
  2. UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
  3. School of Physical Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
  4. Graduate School of Frontier Biosciences, and Department of Physics, Osaka University 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan
Title An investigation of electron-phonon coupling via phonon dispersion measurements in graphite using angle-resolved photoelectron spectroscopy
Laboratory Photophysics Laboratory 〈Prof. Kimura〉
Abstract Electron-phonon coupling (EPC) plays an important role in solid state physics. Here, we demonstrate an experimental method that enables investigation of the elemental processes of the indirect transition, in which EPC participates in photoexcitation in solids, by resolving the energy and momentum of phonons and electrons simultaneously. For graphite, we used angle-resolved photoelectron spectroscopy to observe electron emission at the Γ-point being scattered from the K-point by a phonon. Energy conservation during phonon emission implies that the step-like structure in the spectrum is near the Fermi level, and angle-resolved measurements revealed phonon dispersions that contribute to EPC because of parallel momentum conservation. The observed phonon branch depends on the photon energy, i.e., the final photoexcitation state; this dependency is partly explained by the selection rule, which is determined by the electron state symmetry for the initial, intermediate, and final states and the phonon.