Many-body interactions in quasi-freestanding graphene

TL;DR

This study investigates many-body interactions in quasi-freestanding graphene at the neutrality point, revealing significant electron-electron and electron-phonon interaction changes and behaviors akin to marginal Fermi liquids.

Contribution

It provides new high-resolution ARPES data showing how many-body interactions evolve in graphene at the Dirac point, challenging traditional Fermi liquid assumptions.

Findings

Strong electron-electron interactions observed

Renormalizations indicative of marginal Fermi liquid behavior

Substantial changes in electron-phonon interactions

Abstract

The Landau-Fermi liquid picture for quasiparticles assumes that charge carriers are dressed by many-body interactions, forming one of the fundamental theories of solids. Whether this picture still holds for a semimetal like graphene at the neutrality point, i.e., when the chemical potential coincides with the Dirac point energy, is one of the long-standing puzzles in this field. Here we present such a study in quasi-freestanding graphene by using high-resolution angle-resolved photoemission spectroscopy. We see the electron-electron and electron-phonon interactions go through substantial changes when the semimetallic regime is approached, including renormalizations due to strong electron-electron interactions with similarities to marginal Fermi liquid behavior. These findings set a new benchmark in our understanding of many-body physics in graphene and a variety of novel materials with Dirac fermions.