Self-energy of electrons in graphite intercalation compounds

We use the dynamical random-phase approximation to study the many-body effects of the stage-1 graphite intercalation compounds (GIC’s). Both intraband and interband interactions are included in calculating the self-energy. For the conduction band of an acceptor-type GIC, the interband interactions are found to cause anomalous structures in both the real and the imaginary parts of the self-energy at small wave vectors. In general, the quasiparticle behavior of GIC’s is qualitatively different from that of an electron gas. But near the Fermi surface, the energy width is proportional to (k-(Formula presented)(Formula presented)ln‖k-(Formula presented)‖, which is similar to that of a two-dimensional electron gas. The many-body effects, which have so far been neglected in the graphite systems, may reduce or increase the effective mass of the Fermi-level states, depending on the Fermi energy of the system. These effects should reveal themselves in various optical and transport measurements.