Strong magnetophonon oscillations in extra-large graphene

TL;DR

This study demonstrates that wider graphene devices exhibit strong magnetophonon oscillations due to resonant electron-phonon interactions, enabling detailed spectroscopic analysis of phonon dispersion in van der Waals heterostructures.

Contribution

The paper reveals that increasing device width in graphene heterostructures uncovers new quantum effects and provides a precise method to study electron-phonon interactions.

Findings

Observation of magnetoresistance oscillations in devices wider than ten micrometres.

Identification of transverse acoustic phonon modes as primary scattering agents.

Accurate determination of graphene's low energy phonon dispersion curves.

Abstract

Van der Waals materials and their heterostructures offer a versatile platform for studying a variety of quantum transport phenomena due to their unique crystalline properties and the exceptional ability in tuning their electronic spectrum. However, most experiments are limited to devices that have lateral dimensions of only a few micrometres. Here, we perform magnetotransport measurements on graphene/hexagonal boron-nitride Hall bars and show that wider devices reveal additional quantum effects. In devices wider than ten micrometres we observe distinct magnetoresistance oscillations that are caused by resonant scattering of Landau-quantised Dirac electrons by acoustic phonons in graphene. The study allows us to accurately determine graphene's low energy phonon dispersion curves and shows that transverse acoustic modes cause most of phonon scattering. Our work highlights the crucial importance of device width when probing quantum effects and also demonstrates a precise, spectroscopic method for studying electron-phonon interactions in van der Waals heterostructures.