  The electronic phase diagram of the weak spin-orbit Mott insulator
(Sr(1-x)Lax)3Ir2O7 is determined via an exhaustive experimental study. Upon
doping electrons via La substitution, an immediate collapse in resistivity
occurs along with a narrow regime of nanoscale phase separation comprised of
antiferromagnetic, insulating regions and paramagnetic, metallic puddles
persisting until x~0.04. Continued electron doping results in an abrupt,
first-order phase boundary where the Neel state is suppressed and a homogenous,
correlated, metallic state appears with an enhanced spin susceptibility and
local moments. As the metallic state is stabilized, a weak structural
distortion develops and suggests a competing instability with the parent
spin-orbit Mott state.
