Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 74: Graphene: Electronic Properties, Structure and Substrate Interaction II (joint session DY, DS, HL, MA, O, TT, organized by O)

TT 74.6: Vortrag

Donnerstag, 23. März 2017, 16:15–16:30, TRE Ma

Strong electron-phonon coupling in the σ band of graphene — Federico Mazzola¹, Thomas Frederiksen², Thiagarajan Balasubramanian³, Philip Hofmann⁴, •Bo Hellsing⁵, and Justin W. Wells¹ — ¹Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway — ²Donostia International Physics Center (DIPC) – UPV/EHU, San Sebastián, Spain — ³MAX IV Laboratory, Lund, Sweden — ⁴Department of Physics, Aarhus University, Denmark — ⁵Department of Physics, University of Gothenburg, Sweden

First-principles studies of the electron-phonon coupling in graphene predict a high coupling strength for the σ band with values of the dimensionless mass-enhancement parameter λ up to 0.9. Near the top of the σ band λ is found to be ≈ 0.7. This value is consistent with the observed kink in the σ band dispersion near the Γ-point in the Brillion zone. The calculations show that the electron-phonon coupling is driven primarily by the optical LO and TO phonon modes in graphene. The photoemission intensity from the σ band is strongly suppressed near the Γ-point due to sublattice interference effects. These effects are removed by taking data in the neighbouring Brioullin zone. By this we have been able to disentangle the influence of sublattice interference and electron-phonon coupling. A rigorous analysis of the experimentally determined complex self-energy further supports the assignment of the observed kink to strong electron-phonon coupling and yields λ ≈ 0.6, in excellent agreement with the calculations.