Phonon surface mapping of graphite: Disentangling quasi-degenerate phonon dispersions

Abstract

The two-dimensional mapping of the phonon dispersions around the K point of graphite by inelastic x-ray scattering is provided. The present work resolves the longstanding issue related to the correct assignment of transverse and longitudinal phonon branches at K. We observe an almost degeneracy of the three TO-, LA-, and LO-derived phonon branches and a strong phonon trigonal warping. Correlation effects renormalize the Kohn anomaly of the TO mode, which exhibits a trigonal warping effect opposite to that of the electronic band structure. We determined the electron-phonon coupling constant to be 166 ͑eV/ Å͒ 2 in excellent agreement to GW calculations. These results are fundamental for understanding angle-resolved photoemission, doubleresonance Raman and transport measurements of graphene-based systems.

Probing the electron-phonon coupling in ozone-doped graphene by Raman spectroscopy

“…(6) and (7) we obtain D 2 K F = 205 (eV /Å) 2 . The latter is close to the EPC value found experimentally from the phonon dispersion around the K point of graphite, 35 and to the computed EPC values of graphene and graphite, when nonlocal exchange-correlation effects are included. 38 Actually, D 2 K F of graphene and graphite are expected to differ slightly due to a large screening effect of the exchange interaction in the latter.…”

“…In order to compare with available calculated and experimental values, we relate the EPCs parameters to the square of the e-ph interaction matrix elements averaged on the Fermi surface, D 2 Γ F and D 2 K F , as follows 18,34 where ω Γ and ω K are the frequencies of the phonons at Γ and K point, respectively. While the value of D 2 K F of graphene and related graphitic structures has been controversial, due to the lack of reliable experimental data of the phonon dispersion around the K point, until recently, 35 the value of D 2 Γ F was obtained 36 by relating it to the measured dispersion of the E g mode near Γ. 37 Then taking D 2 Γ F = 39 (eV /Å) 2 , from Eqs.…”

Emergent Chern-Simons excitations due to electron-phonon interaction

“…In the continuous limit the phonons couple to the spinors via combinations of non-diagonal Pauli matrices σ 1 ± iσ 2 with the coupling strength α. While the phonon frequency γ ∼ 160 − 170meV is intrinsic to the hexagonal lattice [17,32,33], the electron-phonon coupling strength α, measured in units energy · length, can be varied in the experiment.…”

Enhanced thermoelectric properties in hybrid graphene/boron nitride nanoribbons

“…Graphene and hexagonal boron nitride (h-BN) are singleatomic-layer honeycomb materials. [10][11][12][13][14][15][16][17][18] Because of the quantum confinement effect, graphene and h-BN exhibit very high electrical conductance and Seebeck coefficient. [19][20][21] However, both pristine graphene and pristine h-BN are poor thermoelectric materials because their thermal conductance is also very high.…”