Featuring nuanced electronic band structure in gapped multilayer graphene

TL;DR

This paper introduces a novel technique to analyze the detailed electronic band structures in multilayer graphene systems, revealing how twist angle and electric field influence flat bands and correlated phases.

Contribution

The authors develop a method to precisely probe the band gap and flat bandwidth evolution in twisted multilayer graphene, enhancing understanding of correlated electronic states.

Findings

Band gap maximizes at specific displacement field

Flat bandwidth minimizes where the gap is largest

Emergence of strongly correlated phase observed

Abstract

Moir\'e systems featuring flat electronic bands exhibit a vast landscape of emergent exotic quantum states, making them one of the resourceful platforms in condensed matter physics in recent times. Tuning these systems via twist angle and the electric field greatly enhances our comprehension of their strongly correlated ground states. Here, we report a technique to investigate the nuanced intricacies of band structures in dual-gated multilayer graphene systems. We utilize the Landau levels of a decoupled monolayer graphene to extract the electric field-dependent bilayer graphene charge neutrality point gap. Then, we extend this method to analyze the evolution of the band gap and the flat bandwidth in twisted mono-bilayer graphene. The band gap maximizes at the same displacement field where the flat bandwidth minimizes, indicating the strongest electron-electron correlation, which is supported by directly observing the emergence of a strongly correlated phase. Moreover, we extract integer and fractional gaps to further demonstrate the strength of this method. Our technique gives a new perspective and paves the way for improving the understanding of electronic band structure in versatile flat band systems.