Plasmon resonance in a sub-THz graphene-based detector: theory and experiment

TL;DR

This study combines experiments and theory to investigate sub-THz plasmon resonances in graphene-based detectors, revealing thermoelectric photovoltage generation and record-low frequency plasmon excitation.

Contribution

It demonstrates the excitation of low-frequency plasmons in bilayer graphene and links them to enhanced photovoltage via a thermoelectric mechanism.

Findings

Photovoltage mainly arises from thermoelectric heating of a p-n junction.

Record-low frequency plasmon resonance at 0.13 THz was observed.

Plasmon excitation enhances electromagnetic field and carrier temperature.

Abstract

We present a combined experimental and theoretical study of photovoltage generation in a bilayer graphene (BLG) transistor structure exposed to subterahertz radiation. The device features a global bottom and split top gate, enabling independent control of the band gap and Fermi level, thereby enabling the formation of a tunable p-n junction in graphene. Measurements show that the photovoltage arises primarily through a thermoelectric mechanism driven by heating of the p-n junction in the middle of the channel. We also provide a theoretical justification for the excitation of two-dimensional plasmons at a record-low frequency of 0.13 THz, which manifests itself as characteristic oscillations in the measured photovoltage. These plasmonic resonances, activated by a decrease in charge carrier concentration due to opening of the band gap, lead to a local enhancement of the electromagnetic field and an increase in the carrier temperature in the junction region. The record-low frequency of plasmon resonance is enabled by the low carrier density achievable in the bilayer graphene upon electrical induction of the band gap.