Microscopic structure of the metal-insulator transition in two dimensions

A single electron transistor is used as a local electrostatic probe to stud y the underlying spatial structure of the metal-insulator transition in two dimensions. The measurements show that as we approach the transition from the metallic side, a new phase emerges that consists of weakly coupled frag ments of the two-dimensional system. These fragments consist of localized c harge that coexists with the surrounding metallic phase. As the density is lowered into the insulating phase, the number of fragments increases on acc ount of the disappearing metallic phase. The measurements reveal that the m etal-insulator transition is a result of the microscopic restructuring that occurs in the system.