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Zone-Boundary Phonon Induced Mini Band Gap Formation in Graphene

We investigate the effect of electron- $\mathrm{A}_{1g}$ phonon coupling on the gapless electronic band dispersion of the pristine graphene. The electron-phonon interaction is introduced through a Kekulé-type distortion giving rise to inter-valley scattering between K and K' points in graphene. We develop a Fröhlich type Hamiltonian within the continuum model in the long wave length limit. By presenting a fully theoretical analysis, we show that the interaction of charge carriers with the highest frequency zone-boundary phonon mode of $% \mathrm{A}_{1g}$-symmetry induces a mini band gap at the corners of the two-dimensional Brillouin zone of the graphene. Since electron-electron interactions favor this type of lattice distortion, it is expected to be enhanced, and thus its quantitative implications might be measurable in graphene.