Propagating Plasmons in a Charge-Neutral Quantum Tunneling Transistor

The ultimate limit of control of light at the nanoscale is the atomic scale. By stacking multiple layers of graphene on hexagonal boron nitride (h-BN), heterostructures with unique nanophotonic properties can be constructed, where the distance between plasmonic materials can be controlled with atom-scale precision. Here we show how an atomically thick tunable quantum tunnelling device can be used as a building block for quantum plasmonics. The device consists of two layers of graphene separated by 1 nm (three monolayers) of h-BN, and a bias voltage between the layers generates an electron gas coupled to a hole gas. We show that, even though its total charge is zero, this system is capable of supporting propagating graphene plasmons.