Disorder in electronic systems is typically modeled as a collection of localized defects, whose distribution is weakly correlated. However, many materials exhibit extended, strongly-correlated defects, such as structural grain boundaries and domain walls.
In my talk, I will show how such extended, correlated defects can dramatically alter dilute 2D metallic systems. We used scanning superconducting quantum interference device (SQUID) microscopy to image the current distribution at the LaAlO_3/SrTiO_3 interface, close to a metal to insulator transition. Our data reveal that the emergence of metallicity in this system is strongly correlated with the presence of tetragonal domain walls in the underlying substrate.
I will present a heuristic model which captures the main features of the data, and discuss the implications of this modelling to the existence of a true critical point in this system.

Collaboration with the groups of: Andrea Caviglia @ TU Delft, Harold Hwang @ Stanford, Kamran Behnia @ CNRS-Paris