A weakly correlated Fermi liquid state with a small Fermi surface in   lightly doped Sr$_3$Ir$_2$O$_7$
  We characterize the electron doping evolution of (Sr$_{1-x}$La$_x$)$_3$Ir$_2$O$_7$ by means of angle-resolved photoemission. Concomitant with the metal insulator transition around $x\approx0.05$ we find the emergence of coherent quasiparticle states forming a closed small Fermi surface of volume $3x/2$, where $x$ is the independently measured La concentration. The quasiparticle weight $Z$ remains large along the entire Fermi surface, consistent with the moderate renormalization of the low-energy dispersion. This indicates a conventional, weakly correlated Fermi liquid state with a momentum independent residue $Z\approx0.5$ in lightly doped Sr$_3$Ir$_2$O$_7&. 
Alberto de la Torre, Emily Claire Hunter, Alaska Subedi, Siobhan   McKeown Walker, Anna Tamai, Timur Kim, Moritz Hoesch, Rob...
cond-mat.str-el