Strong Coulomb drag and broken symmetry in double-layer graphene

Understand

Spatially separated electron systems remain strongly coupled by electron-electron interactions even when they cannot exchange particles, provided that the layer separation d is comparable to a characteristic distance l between charge carriers within layers.

• One of the consequences of this remote coupling is a phenomenon called Coulomb drag, in which an electric current passed through one of the layers causes frictional charge flow in the other layer.
• Previously, only the regime of weak (d>>l) to intermediate (d ~ l) coupling could be studied experimentally.
• Here we use graphene-BN heterostructures with d down to 1 nm to probe interlayer interactions and Coulomb drag in the limit d<<l where the two Dirac liquids effectively nest within the same plane, but still can be tuned and measured independently.