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 inte rband 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 dif ferent from that of an electron gas. But near the Fermi surface, the e nergy width is proportional to (k-k(F))(2)ln\k-k(F)\, which is similar to that of a two-dimensional electron gas. The many-body effects, whi ch have so far been neglected in the graphite systems, may reduce or i ncrease 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.