  A correlated material in the vicinity of an insulator-metal transition (IMT)
exhibits rich phenomenology and variety of interesting phases. A common avenue
to induce IMTs in Mott insulators is doping, which inevitably leads to
disorder. While disorder is well known to create electronic inhomogeneity,
recent theoretical studies have indicated that it may play an unexpected and
much more profound role in controlling the properties of Mott systems. Theory
predicts that disorder might play a role in driving a Mott insulator across an
IMT, with the emergent metallic state hosting a power law suppression of the
density of states (with exponent close to 1; V-shaped gap) centered at the
Fermi energy. Such V-shaped gaps have been observed in Mott systems but their
origins are as yet unknown. To investigate this, we use scanning tunneling
microscopy and spectroscopy to study isovalent Ru substitutions in
Sr$_3$(Ir$_{1-x}$Ru$_x$)$_2$O$_7$ which drives the system into an
antiferromagnetic, metallic state. Our experiments reveal that many core
features of the IMT such as power law density of states, pinning of the Fermi
energy with increasing disorder, and persistence of antiferromagnetism can be
understood as universal features of a disordered Mott system near an IMT and
suggest that V-shaped gaps may be an inevitable consequence of disorder in
doped Mott insulators.
