Kohn Anomalies and Electron-Phonon Interactions in Graphite

We demonstrate that graphite phonon dispersions have two Kohn anomalies at the $\ensuremath{\Gamma}\mathrm{\text{\ensuremath{-}}}{E}_{2g}$ and $\mathbf{K}\mathrm{\text{\ensuremath{-}}}{A}_{1}^{\ensuremath{'}}$ modes. The anomalies are revealed by two sharp kinks. By an exact analytic derivation, we show that the slope of these kinks is proportional to the square of the electron-phonon coupling (EPC). Thus, we can directly measure the EPC from the experimental dispersions. The $\ensuremath{\Gamma}\mathrm{\text{\ensuremath{-}}}{E}_{2g}$ and $\mathbf{K}\mathrm{\text{\ensuremath{-}}}{A}_{1}^{\ensuremath{'}}$ EPCs are particularly large, while they are negligible for all the other modes at $\ensuremath{\Gamma}$ and…