Amplified-reflection plasmon instabilities in grating-gate plasmonic crystals

TL;DR

This paper investigates a mechanism for plasmon instabilities in periodically gated two-dimensional electron systems, revealing how amplified reflection at boundaries can lead to controllable instabilities with potential applications in plasmonic devices.

Contribution

It introduces a new instability mechanism based on amplified reflection in plasmonic crystals and derives a generic dispersion relation for these structures.

Findings

Threshold drift velocity can be tuned below plasmon phase velocity.

Plasmon increment can surpass collisional damping rates.

Instability is achievable at room temperature in graphene.

Abstract

We identify a possible mechanism of the plasmon instabilities in periodically gated two-dimensional electron systems with a modulated electron density (plasmonic crystals) under direct current. The instability occurs due to the amplified reflection of the small density perturbations from the gated/ungated boundaries under the proper phase matching conditions between the crystal unit cells. Based on the transfer-matrix formalism, we derive the generic dispersion equation for the travelling plasmons in these structures. Its solution in the hydrodynamic limit shows that the threshold drift velocity for the instability can be tuned below the plasmon phase and carrier saturation velocities, and the plasmon increment can exceed the collisional damping rate typical to III-V semiconductors at 77 K and graphene at room temperature.