Weak localization and universal conductance fluctuations in large area twisted bilayer graphene

TL;DR

This study reports the first observation of weak localization and universal conductance fluctuations in large area twisted bilayer graphene, revealing insights into quantum interference effects and scattering mechanisms.

Contribution

It demonstrates weak localization in twisted bilayer graphene and analyzes phase coherence and scattering lengths, advancing understanding of quantum transport in moiré materials.

Findings

Weak localization observed in all samples, allowing extraction of phase coherence and scattering lengths.

Universal conductance fluctuations detected in high-mobility, near van Hove singularity sample.

Dephasing caused by electron-electron scattering; intervalley scattering caused by point defects.

Abstract

We study diffusive magnetotransport in highly p-doped large area twisted bilayer graphene in 1{\deg}, 7{\deg}, 9{\deg} and 20{\deg} samples. We report weak localization in twisted bilayer graphene for the first time. All samples exhibit weak localization, from which we extract the phase coherence length and intervalley scattering lengths, and from that determine that dephasing is caused by electron-electron scattering and intervalley scattering is caused by point defects. We observe signatures of universal conductance fluctuations in the 9{\deg} sample, which has high mobility and is near the van Hove singularity. Further improvements in sample quality and applications to large area moire materials will open new avenues to observe quantum interference effects.