Quasiparticle lifetime in graphite studied by ultrahigh-resolution ARPES

Abstract We have performed ultrahigh-resolution angle-resolved photoemission spectroscopy (ARPES) to elucidate the nature of quasiparticle dynamics in graphite. We found fairly sharp quasiparticle peak of π band around K ( H ) point in the vicinity of the Fermi level, together with the strong mass renormalization of the band (kink). The imaginary part of electron self-energy (Im Σ ) shows a sudden drop below 0.18 eV, indicative of a strong electron–phonon coupling. The linear energy dependence of Im Σ at higher binding energies provides an evidence for the deviation from the conventional Fermi liquid theory.