Plasmon-phonon coupled modes in graphene tuned by the carrier concentration of the semiconductor substrates

TL;DR

This paper explores how the interaction between graphene plasmons and semiconductor substrate phonons can be tuned by adjusting the substrate's carrier concentration, affecting the energy, momentum, and lifetime of coupled modes.

Contribution

It introduces a new mechanism to control plasmon-phonon coupled modes via carrier injection in semiconductor substrates, impacting their dispersion and lifetime.

Findings

PPCM energy increases with substrate carrier concentration.

PPCM momentum decreases as carrier concentration increases.

Lifetime of PPCMs exceeds that of uncoupled graphene plasmons.

Abstract

The interaction between graphene plasmons and surface phonons of a semiconductor substrate is investigated, which can be efficiently controlled by the carrier injection of the substrate. The energy and lifetime of surface phonons in a substrate depend a lot on the carrier concentration, which provides a new machanism to tune plasmon-phonon coupled modes (PPCMs). More specifically, the dispersion and lifetime of PPCMs can be controlled by the carrier concentration change of the substrate. The energy of PPCMs for a given momentum increases as the carrier concentration of a substrate increases. On the other hand, the momentum of PPCMs for a given energy decreases when the carrier concentration of the substrate increases. Lifetime of PPCMs is always larger than the intrinsic lifetime of graphene plasmons without plasmon-phonon coupling.