Transfer of spectral weight across the gap of Sr2IrO4 induced by la doping

We study with angle-resolved photoelectron spectroscopy the evolution of the electronic structure of Sr2IrO4, when holes or electrons are introduced, through Rh or La substitutions. At low dopings, the added carriers occupy the first available states, at the bottom or top of the gap, revealing an asymmetric gap of 0.7 eV, in good agreement with scanning tunnel microscope measurements. At further doping, we observe a reduction of the gap and a transfer of spectral weight across the gap, although the quasiparticle weight remains very small. We discuss the origin of the in-gap spectral weight as a local distribution of gap values.