Imaging and tuning polarity at SrTiO domain walls.

Electrostatic fields tune the ground state of interfaces between complex oxide materials. Electronic properties, such as conductivity and superconductivity, can be tuned and then used to create and control circuit elements and gate-defined devices. Here we show that naturally occurring twin boundaries, with properties that are different from their surrounding bulk, can tune the LaAlO/SrTiO interface 2DEG at the nanoscale. In particular, SrTiO domain boundaries have the unusual distinction of remaining highly mobile down to low temperatures, and were recently suggested to be polar. Here we apply localized pressure to an individual SrTiO twin boundary and detect a change in LaAlO/SrTiO interface current distribution. Our data directly confirm the existence of polarity at the twin boundaries, and demonstrate that they can serve as effective tunable gates. As the location of SrTiO domain walls can be controlled using external field stimuli, our findings suggest a novel approach to manipulate SrTiO-based devices on the nanoscale.