  Materials that exhibit both strong spin orbit coupling and electron
correlation effects are predicted to host numerous new electronic states. One
prominent example is the Jeff =1/2 Mott state in Sr2IrO4, where introducing
carriers is predicted to manifest high temperature superconductivity analogous
to the S=1/2 Mott state of La2CuO4. While bulk superconductivity currently
remains elusive, anomalous quasi-particle behaviors paralleling those in the
cuprates such as pseudogap formation and the formation of a d-wave gap are
observed upon electron-doping Sr2IrO4. Here we establish a magnetic parallel
between electron-doped Sr2IrO4 and hole-doped La2CuO4 by unveiling a spin
density wave state in electron-doped Sr2IrO4. Our magnetic resonant x-ray
scattering data reveal the presence of an incommensurate magnetic state
reminiscent of the diagonal spin density wave state observed in the monolayer
cuprate (La1-xSrx)2CuO4. This link supports the conjecture that the quenched
Mott phases in electron-doped Sr2IrO4 and hole-doped La2CuO4 support common
competing electronic phases.
