Electron-doped Sr ₂IrO _4?δ (0<δ<0.04): Evolution of a disordered Jeff= 1/2 Mott insulator into an exotic metallic state

Stoichiometric Sr ₂IrO ₄ is a ferromagnetic J _eff = 1/2 Mott insulator driven by strong spin-orbit coupling. Introduction of very dilute oxygen vacancies into single-crystal Sr ₂ IrO _4-δ with δ≤0.04 leads to significant changes in lattice parameters and an insulator-to-metal transition at T _MI =105 K. The highly anisotropic electrical resistivity of the low-temperature metallic state for δ≈0.04 exhibits anomalous properties characterized by non-Ohmic behavior and an abrupt current-induced transition in the resistivity at T ^* =52K, which separates two regimes of resistive 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 ∼10mA/ cm ² (compared to higher spin-torque currents ∼ 10 ⁷ - 10 ⁸ A/ cm ²) or magnetic inductions ∼0.1-1.0T.