Plasmon induced thermoelectric effect in graphene

TLDR

Graphene is a promising optoelectronic material whose photoresponse includes photovoltaic and dominant hot‑carrier photothermoelectric effects that depend on Seebeck coefficient variations, and a second photothermoelectric effect can arise across a homogeneous channel when an electronic temperature gradient is present. The study investigates plasmon‑induced photothermoelectric currents in graphene driven by localized plasmonic heating near nanostructured contacts, aiming to isolate this effect at electronic temperatures around 2000 K. The authors use nanostructured electrical contacts to generate localized plasmonic heating, raising graphene carrier temperatures to ~2000 K and creating a pronounced electronic temperature gradient. In this regime, the device functions as a sensitive electronic thermometer, demonstrating that plasmon‑induced photothermoelectric currents can be harnessed for hot‑carrier plasmonic applications.

Abstract

Graphene has emerged as a promising material for optoelectronics due to its potential for ultrafast and broad-band photodetection. The photoresponse of graphene junctions is characterized by two competing photocurrent generation mechanisms: a conventional photovoltaic effect and a more dominant hot-carrier-assisted photothermoelectric (PTE) effect. The PTE effect is understood to rely on variations in the Seebeck coefficient through the graphene doping profile. A second PTE effect can occur across a homogeneous graphene channel in the presence of an electronic temperature gradient. Here, we study the latter effect facilitated by strongly localised plasmonic heating of graphene carriers in the presence of nanostructured electrical contacts resulting in electronic temperatures of the order of 2000 K. At certain conditions, the plasmon-induced PTE photocurrent contribution can be isolated. In this regime, the device effectively operates as a sensitive electronic thermometer and as such represents an enabling technology for development of hot carrier based plasmonic devices.