Electrical plasmon injection in double-layer graphene heterostructures

It is by now well established that high-quality graphene enables a gate-tunable low-loss plasmonic platform for the efficient confinement, enhancement, and manipulation of optical fields spanning a broad range of frequencies, from the midinfrared to the terahertz domain. While all-electrical detection of graphene plasmons has been demonstrated, electrical plasmon injection, which is crucial to operate nanoplasmonic devices without the encumbrance of a far-field optical apparatus, remains elusive. In this work, we present a theory of electrical plasmon injection in double-layer graphene, where a vertical tunnel current excites acoustic and optical plasmon modes. We first calculate the power delivered by the applied interlayer voltage bias into these collective modes. We then show that this system works also as a spectrally resolved molecular sensor.