Scanning SQUID investigation of SrTiO3 domain walls

The interface between the oxide insulators LaAlO₃ and SrTiO₃ hosts a gate tunable 2D electron gas that also becomes SC at low temperatures. It has been demonstrated that the 2DEG can be confined to create devices such as gate defined SQUIDs or a single electron transistor.

In effect the Physics of the SrTiO₃ substrate play a major role in the behavior of the interface. SrTiO₃ undergoes a structural phase transition at 105K resulting in a dense network of domains separated by nano-meter thick twin walls.

I will discuss our recent findings, where we used scanning SQUID microscopy to map the spatial distribution of conduction at the interface. Images of the interface showed channels of modulated current flow, superconductivity and magnetic signal. The domain walls change their location with thermal cycles and with the application of back gate voltage. In addition we observed that the domain wall behavior changes with application of stress. These findings open exciting possibilities for normal and superconducting devices based on domain walls