Electron-dopedSr2IrO4−δ(0≤δ≤0.04): Evolution of a disorderedJeff=12Mott insulator into an exotic metallic state

Abstract

Stoichiometric ${\text{Sr}}_{2}{\text{IrO}}_{4}$ is a ferromagnetic ${J}_{\text{eff}}=\frac{1}{2}$ Mott insulator driven by strong spin-orbit coupling. Introduction of very dilute oxygen vacancies into single-crystal ${\text{Sr}}_{2}{\text{IrO}}_{4\ensuremath{-}\ensuremath{\delta}}$ with $\ensuremath{\delta}\ensuremath{\le}0.04$ leads to significant changes in lattice parameters and an insulator-to-metal transition at ${T}_{\text{MI}}=105\text{ }\text{K}$. The highly anisotropic electrical resistivity of the low-temperature metallic state for $\ensuremath{\delta}\ensuremath{\approx}0.04$ exhibits anomalous properties characterized by non-Ohmic behavior and an abrupt current-induced transition in the resistivity at ${T}^{\ensuremath{\ast}}=52\text{ }\text{K}$, which separates two regimes of resistive switching in the nonlinear $I\text{\ensuremath{-}}V$ 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 $\ensuremath{\sim}10\text{ }\text{mA}/{\text{cm}}^{2}$ (compared to higher spin-torque currents $\ensuremath{\sim}{10}^{7}--{10}^{8}\text{ }\text{A}/{\text{cm}}^{2}$) or magnetic inductions $\ensuremath{\sim}0.1--1.0\text{ }\text{T}$.