Acoustic plasmons and "soundarons" in graphene on a metal gate

TL;DR

This paper reveals that graphene with a metal gate supports a gapless, linearly dispersing acoustic plasmon mode and exhibits unique satellite features called soundarons in its quasiparticle spectrum, observable via spectroscopy.

Contribution

It provides an exact calculation of the acoustic plasmon velocity and predicts the existence of soundarons in graphene-metal systems, advancing understanding of collective excitations and spectral features.

Findings

Graphene on a metal gate supports a gapless acoustic plasmon mode.

The quasiparticle spectrum shows satellite bands called soundarons.

Soundarons can be observed using angle-resolved photoemission spectroscopy.

Abstract

We demonstrate that single-layer graphene in the presence of a metal gate displays a gapless collective (plasmon) mode that has a linear dispersion at long wavelengths. We calculate exactly the acoustic-plasmon group velocity at the level of the random phase approximation and carry out microscopic calculations of the one-body spectral function of such system. Despite screening exerted by the metal, we find that graphene's quasiparticle spectrum displays a very rich structure characterized by composite hole-acoustic plasmon satellite bands (that we term for brevity "soundarons"), which can be observed by e.g. angle-resolved photoemission spectroscopy.