Poster

Strong electron-phonon coupling in the σ-band of graphene

T. Frederiksen^1,2, F. Mazzola³, J. Wells³, T. Balasubramanian⁴, and B. Hellsing^1,5

¹Donostia International Physics Center (DIPC) – UPV/EHU, E-20018 San Sebastián, Spain

²IKERBASQUE, Basque Foundation for Science, E-48013, Bilbao, Spain

³Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway

⁴MAX-lab, PO Box 118, S-22100 Lund, Sweden

⁵Material and Surface Theory Group, Department of Physics, University of Gothenburg, Sweden

We present a first-principles study of the electron-phonon (e-ph) coupling strength in free-standing graphene. We analyze it in terms of the dimensionless mass enhancement parameter λ, resolved in terms of final-state electron energy for a photohole created in either a σ- or a π-band, using the SIESTA code [1] in combination with a finite-difference scheme for the e-ph coupling [2,3]. Our calculations show that λ_σ is significantly greater than λ_π. Near the top of the σ valence band we obtain λ_σ ≈ 0.8 in agreement with recent angle-resolved photoemission spectroscopy (ARPES) experiments [4].

As proposed in the experimental work, we confirm that the longitudinal optical phonons provide the most essential contribution to the exceptionally large λ_σ value. However, we also find an important contribution to λ_σ and λ_π from the interband scattering π→σ and σ→π, respectively, mediated by the out-of-plane phonons. Finally, we also explore the role of strain which turns out to diminish the interband scattering.

[1] J. M. Soler et al., J. Phys.: Condens. Matter 14, 2745 (2002)

[2] https://sourceforge.net/projects/inelastica

[3] T. Frederiksen et al., Phys. Rev. B 75, 205413 (2007)

[4] F. Mazzola et al., Phys. Rev. Lett. 111, 216806 (2013)