Optical Characterization of Electron-Phonon Interactions at the Saddle Point in Graphene

The role of many-body interactions is experimentally and theoretically investigated near the saddle point absorption peak of graphene. The time and energy-resolved differential optical transmission measurements reveal the dominant role played by electron-acoustic phonon coupling in band structure renormalization. Using a Born approximation for electron-phonon coupling and experimental estimates of the dynamic lattice temperature, we compute the differential transmission line shape. Comparing the numerical and experimental line shapes, we deduce the effective acoustic deformation potential to be D-eff(ac) similar or equal to 5 eV. This value is in accord with recent theoretical predictions but differs from those extracted using electrical transport measurements.