Quasiparticles, plasmarons, and quantum spectral function in bilayer graphene

We theoretically study the many-body effects of electron-electron interaction on the single-particle spectral function of doped bilayer graphene (BLG). Using random-phase approximation, we calculate the real and imaginary parts of the self-energy and, hence, the spectral function. The spectral function near the Fermi surface shows the usual quasiparticle (QP) peak, establishing doped BLG, in contrast to the unstable neutral system, to be a Fermi liquid. Away from the Fermi surface, an additional broad plasmaron peak is visible in the spectral function. From the low-energy behavior of the self-energy, we calculate the QP residue and the effective mass of the QPs as a function of carrier density. We present the results for the QP renormalization within the on-shell as well as the off-shell approximations.