Strong plasmon-phonon splitting and hybridization in 2D materials revealed through a self-energy approach

TL;DR

This paper predicts strong plasmon-phonon hybridization and avoided crossing in 2D materials using a self-energy approach, revealing new spectral features and providing a computationally efficient method for studying such interactions.

Contribution

It introduces a self-energy based formalism for analyzing plasmon-phonon interactions in 2D materials, capturing strong coupling effects and spectral splittings.

Findings

Predicted strong plasmon splitting due to phonon coupling

Observed radical spectral modifications in doped graphene nanotriangles

Demonstrated applicability to various 2D materials

Abstract

We reveal new aspects of the interaction between plasmons and phonons in 2D materials that go beyond a mere shift and increase in plasmon width due to coupling to either intrinsic vibrational modes of the material or phonons in a supporting substrate. More precisely, we predict strong plasmon splitting due to this coupling, resulting in a characteristic avoided crossing scheme. We base our results on a computationally efficient approach consisting in including many-body interactions through the electron self-energy. We specify this formalism for a description of plasmons based upon a tight-binding electron Hamiltonian combined with the random-phase approximation. This approach is accurate provided vertex corrections can be neglected, as is is the case in conventional plasmon-supporting metals and Dirac-fermion systems. We illustrate our method by evaluating plasmonic spectra of doped graphene nanotriangles with varied size, where we predict remarkable peak splittings and other radical modifications in the spectra due to plasmons interactions with intrinsic optical phonons. Our method is equally applicable to other 2D materials and provides a simple approach for investigating coupling of plasmons to phonons, excitons, and other excitations in hybrid thin nanostructures.