Thermoelectric detection and imaging of propagating graphene plasmons

A device is presented that can detect mid-infrared plasmons in graphene encapsulated by hexagonal boron nitride via the thermoelectric effect; the natural decay product of the plasmons (electronic heat) is converted into a measurable voltage signal. Controlling, detecting and generating propagating plasmons by all-electrical means is at the heart of on-chip nano-optical processing 1 , 2 , 3 . Graphene carries long-lived plasmons that are extremely confined and controllable by electrostatic fields 4 , 5 , 6 , 7 ; however, electrical detection of propagating plasmons in graphene has not yet been realized. Here, we present an all-graphene mid-infrared plasmon detector operating at room temperature, where a single graphene sheet serves simultaneously as the plasmonic medium and detector. Rather than achieving detection via added optoelectronic materials, as is typically done in other plasmonic systems 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , our device converts the natural decay product of the plasmon—electronic heat—directly into a voltage through the thermoelectric effect 16 , 17 . We employ two local gates to fully tune the thermoelectric and plasmonic behaviour of the graphene. High-resolution real-space photocurrent maps are used to investigate the plasmon propagation and interference, decay, thermal diffusion, and thermoelectric generation.