Spin density wave order and its influence on the unconventional metallic states in carrier-doped Sr_n+1Ir_nO_3n+1 systems

The discovery of spin-orbit assisted or J_eff=1/2 Mott insulating states in select 4d and 5d transition metal oxides has fueled a number of predictions of novel electronic phases that emerge once the parent Mott phase is quenched. Depending on the structure type, examples of these phases span from unconventional superconductivity to new manifestations of correlated topological electronic states. The seminal examples of J_eff=1/2 Mott states found in the homologous Ruddlesden-Popper series Sr_n+1Ir_nO_3n+1 are a versatile platform for understanding the mechanism for the collapse of the Mott state as the J_eff=1/2 band is driven away from half filling and for resolving the presence of nearby electronic instabilities. In this talk, I will present some of our recent work exploring the competing states accessed via chemically doping these compounds. Upon electron-doping into Sr₂IrO₄ and hole-doping into Sr₃Ir₂O₇, spin density wave states emerge and provide clues to the nature of the unconventional metals that form in each. A “diagonal” spin density wave state analogous to those formed in the underdoped high-T_c cuprates appears in electron-doped Sr₂IrO₄ and suggests a link between the competing ground states of La_2-xSr_xCuO4 and Sr_2-xLa_xIrO₄. In hole-doped Sr₃Ir₂O₇, the slow collapse of the Mott state reveals an intermediate strange metal regime where spin density wave order survives beyond the collapse of the Mott charge gap. I will discuss these two examples and the implications of each in understanding the phase diagrams of more strongly correlated Mott states.