Electron-phonon coupling in potassium-doped graphene: Angle-resolved photoemission spectroscopy

The electron-phonon coupling in potassium-doped graphene on Ir(111) is studied via the renormalization of the ${\pi }^{\ast }$ band near the Fermi level, using angle-resolved photoemission spectroscopy. The renormalization is found to be fairly weak and almost isotropic, with a mass enhancement parameter of $\lambda =0.28\left(6\right)$ for both the $\overline{K}-\overline{M}$ and the $\overline{K}-\overline{\Gamma }$ direction. These results are found to agree well with recent first-principles calculations.

Figure 1

Photoemission intensity around the $\overline{K}$ point shown as different cuts through a three-dimensional data set. (a) Large-scale dispersion through $\overline{K}$. (b) Fermi surface around $\overline{K}$ with the dashed line indicating the cut shown in (a). More detailed Fermi energy crossings along the $\overline{K}\text{−}\overline{\Gamma }$(c) and $\overline{K}\text{−}\overline{M}$(d) directions. (e) and (f) show the simulated photoemission intensity corresponding to the data in (c) and (d), respectively.

Figure 2

(Color online) Detailed comparison between the measured spectral functions and those found in the iterative optimization procedure outlined here. (a) and (c) peak position in MDC cuts together with the bare dispersion obtained from the fit (dashed line); (b) and (d) peak full width at half maximum. Points with error bars represent data, solid lines the fit.

Figure 3

(Color online) Optimized self-energies (real part ${\Sigma }^{\prime }$ and imaginary part ${\Sigma }^{″}$) for the $\overline{K}\text{−}\overline{\Gamma }$(a) and $\overline{K}\text{−}\overline{M}$(b) directions.