In a Quantum Hall System, Is the Insulator Really a Conductor in Vortex Clothing?

Dan Shahar, Daniel Tsui and Mansour Shayegan at Princeton University were studying the liquid‐to‐insulator transitions in a quantum Hall system recently when they noticed a surprising symmetry in the plot of longitudinal voltage versus current: For each point close to the phase transition in the liquid phase, they could find a corresponding point in the insulating phase such that the (normalized) I–V curve for one fell precisely on the V‐I curve of the other—that is, the curve with the voltage and current coordinates switched. Such behavior suggests that the underlying dynamics of the liquid and insulator phases must be intimately related, despite their overtly different transport characteristics.