Electron-Doped Sr2IrO4-delta (0 <= delta <= 0.04): Evolution of a Disordered Jeff = 1/2 Mott Insulator into an Exotic Metallic State

Abstract: Stoichiometric Sr2IrO4 is a ferromagnetic Jeff = 1/2 Mott insulator driven by strong spin-orbit coupling. Introduction of very dilute oxygen vacancies into single-crystal Sr2IrO4-delta with delta < 0.04 leads to significant changes in lattice parameters and an insulator-to-metal transition at TMI = 105 K. The highly anisotropic electrical resistivity of the low-temperature metallic state for delta ~ 0.04 exhibits anomalous properties characterized by non-Ohmic behavior and an abrupt current-induced transition in the resistivity at T* = 52 K, which separates two regimes of resisitive switching in the nonlinear I-V characteristics. The novel behavior illustrates an exotic ground state and constitutes a new paradigm for devices structures in which electrical resistivity is manipulated via low-level current densities ~ 10 mA/cm2 (compared to higher spin-torque currents ~ 107-108 A/cm2) or magnetic inductions ~ 0.1-1.0 T.