Graphene plasmon-phonon coupled modes at the exceptional point

TL;DR

This paper investigates the coupling between graphene plasmons and phonons, identifying the exceptional point where the transition between strong and weak coupling occurs, and explores its implications for sensing and mode control.

Contribution

It introduces a non-Hermitian framework to analyze the coupling transition and demonstrates how to observe this transition through various experimental parameters.

Findings

Identified the exceptional point as the transition between strong and weak coupling.

Enhanced sensitivity to perturbations near the exceptional point.

Transition observable by changing incident radiation angle.

Abstract

Properties of graphene plasmons are greatly affected by their coupling to phonons. While such coupling has been routinely observed in both near-field and far-field graphene spectroscopy, the interplay between coupling strength and mode losses, and its exceptional point physics has not been discussed. By applying a non-Hermitian framework, we identify the transition point between strong and weak coupling as the exceptional point. Enhanced sensitivity to perturbations near the exceptional point is observed by varying the coupling strength and through gate modulation of the graphene Fermi level. Finally, we also show that the transition from strong to weak coupling is observable by changing the incident angle of radiation.