Electron-phonon coupling in a magic-angle twisted-bilayer graphene device

TL;DR

This study investigates how electron-phonon interactions in magic-angle twisted bilayer graphene influence its correlated electronic phenomena, using Raman spectroscopy and atomistic modeling to reveal unique doping and coupling behaviors.

Contribution

It demonstrates the role of electron-phonon coupling in magic-angle TBG and links it to observed strongly correlated phenomena, supported by experimental and theoretical analysis.

Findings

Magic-angle TBG shows asymmetric doping behavior.

Electron-phonon coupling affects G band linewidth.

Modeling aligns with experimental observations.

Abstract

The importance of phonons in the strong correlation phenomena observed in twisted bilayer graphene (TBG) at the so-called magic-angle is under debate. Here we apply gate-dependent micro-Raman spectroscopy to monitor the G band linewidth in TBG devices of twist angles $\theta=0^{\circ}$, $\sim 1.1^{\circ}$ (magic-angle) and $\sim 7^{\circ}$ (large angle). The results show a broad and p/n-asymmetric doping behavior at the magic-angle, in clear contrast to the behavior observed in twist angles above and below. Atomistic modeling reproduces the experimental observations, revealing how the unique electronic structure of magic-angle TBGs influences the electron-phonon coupling and, consequently, the G band linewidth. Our findings indicate a connection between electron-phonon coupling and experimental observations of strongly correlated phenomena in magic-angle TBG.