Coherent quasiparticles in lightly doped Sr3Ir2O7

We characterize the electron doping evolution of (Sr1−xLax)3Ir2O7. Concomitant with the metal insulator transition around x≈0.05 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, and no pseudogap is observed.