Many-particle effects in the cyclotron resonance of encapsulated monolayer graphene

TL;DR

This study reveals that electron-electron interactions significantly influence Landau level transition energies in encapsulated monolayer graphene, with observed non-monotonic behavior and a Dirac mass splitting due to lattice coupling.

Contribution

It provides direct experimental evidence of many-particle effects in graphene's cyclotron resonance, highlighting the role of electron interactions and lattice coupling.

Findings

Transition energies depend non-monotonically on Landau level filling factor.

Observation of a splitting interpreted as a Dirac mass from lattice coupling.

Electron-electron interactions affect Landau level transitions beyond single-particle models.

Abstract

We study the infrared cyclotron resonance of high mobility monolayer graphene encapsulated in hexagonal boron nitride, and simultaneously observe several narrow resonance lines due to interband Landau level transitions. By holding the magnetic field strength, $B$, constant while tuning the carrier density, $n$, we find the transition energies show a pronounced non-monotonic dependence on the Landau level filling factor, $\nu\propto n/B$. This constitutes direct evidence that electron-electron interactions contribute to the Landau level transition energies in graphene, beyond the single-particle picture. Additionally, a splitting occurs in transitions to or from the lowest Landau level, which is interpreted as a Dirac mass arising from coupling of the graphene and boron nitride lattices.