Electrically tunable transport in antiferromagnetic Sr$_{2}$IrO$_{4}$

Electronic transport in antiferromagnetic (AFM) Mott insulator Sr$_{2}$IrO$_{4}$ is studied under high electric fields. Our goal is to address the question of electronic conduction in nano-scale AFM spintronic applications [1] where high biases and associated electric fields are routinely present. We use nano-scale contacts between a sharpened Cu tip and single crystal of Sr$_{2}$IrO$_{4}$ to achieve electric fields up to a few MV/m. When an electrical bias is applied to such a point contact, the electric potential drops essentially in a small contact region, thus leading to high electric fields and providing a means to probe electronic transport on a microscopic scale. Detailed measurements of point-contact current-voltage characteristics revealed that the contact resistance decreased significantly (50-70{\%}) with an increasing dc bias. The observed bias dependence can be well fitted by an activation energy model that involves band structure modifications under strong electric fields. Our findings suggest a promising path towards band-gap engineering in 5d transition metal oxides, which may lead to appealing technical solutions in developing next generation's electronic devices.\\[4pt] [1] C. Wang et al., Phys. Rev. X, November 2014.