  The physics of doped Mott insulators remains controversial after decades of
active research, hindered by the interplay among possible competing orders and
fluctuations. It is thus highly desired to distinguish the intrinsic characters
of the Mott-metal crossover from those of other origins. We investigate the
evolution of electronic structure and dynamics of the hole-doped J=1/2 Mott
insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with
Rh atoms, with the chemical potential immediately jumping to or near the top of
the lower Hubbard band. The doped iridates exhibit multiple exotic features
previously observed in doped cuprates - pseudogaps, Fermi "arcs", and
marginal-Fermi-liquid-like electronic scattering rates, despite different
mechanisms that forbid electron double-occupancy. We argue these universal
features of the Mott-metal crossover are not related to preformed electron
pairing, quantum criticality or density-wave formation as most commonly
discussed. Instead, short-range antiferromagnetic correlations may play an
indispensible role.
