The effect of electric field on the 2D interface between LaAlO₃ and SrTiO₃ has been extensively studied by transport measurements. Electric fields tune conductivity, carrier density and mobility, leading to a metal-insulator transition. Spatial maps of the electronic properties of the interface near the transition can provide insights to the critical behavior.

We use scanning superconducting quantum interference device to map the conduction landscape in LaAlO₃/SrTiO₃ samples, in the presence of electric field applied by a back gate. We obtain real-space images of the system’s conductivity landscape near the metal-insulator transition. Our measurements reveal that defects play an important role in the transition, and that different types of defects may lead to surprisingly different behaviors near the insulating regime.

Collaborations: Andrea Caviglia @ TU Delft (samples), Harold Hwang @ Stanford (samples), Jonathan Ruchman @ BIU (theory).