Unidirectional spin density wave state in metallic (Sr(1−x)La(x))(2)IrO(4)

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 J(eff) = 1/2 Mott state in Sr(2)IrO(4), where introducing carriers is predicted to manifest high temperature superconductivity analogous to the S = 1/2 Mott state of La(2)CuO(4). While bulk superconductivity currently remains elusive, anomalous quasiparticle behaviors paralleling those in the cuprates such as pseudogap formation and the formation of a d-wave gap are observed upon electron-doping Sr(2)IrO(4). Here we establish a magnetic parallel between electron-doped Sr(2)IrO(4) and hole-doped La(2)CuO(4) by unveiling a spin density wave state in electron-doped Sr(2)IrO(4). 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 (La(1−x)Sr(x))(2)CuO(4). This link supports the conjecture that the quenched Mott phases in electron-doped Sr(2)IrO(4) and hole-doped La(2)CuO(4) support common competing electronic phases.