Low-lying electronic structure of triangular cobaltite

We report detailed Fermi surface topology and quasiparticle dynamics of the host cobaltate Na0.7CoO2. A direct mapping of the Fermi surface is carried out by angle-resolved photoemission spectroscopy (ARPES). Fermi surface at 16 K is a hole-pocket centered around the Γ-point. A highly correlated nature of the electron liquid in this system is evidenced from strong on-site Coulomb interaction seen through a valence satellite and via renormalization of the quasiparticle dispersion. The quasiparticle band disperses less than 100 meV and exists in the T-linear regime of resistivity up to 120 K.