Flat Band and Many-body Gap in Chirally Twisted Triple Bilayer Graphene

TL;DR

This paper experimentally confirms the existence of flat bands and energy gaps in chirally twisted triple bilayer graphene, revealing potential Coulomb interaction effects and providing a new approach to study moiré systems.

Contribution

It introduces the first experimental observation of flat bands and energy gaps in this novel moiré structure, advancing understanding of correlated phenomena in twisted multilayer graphene.

Findings

Confirmed flat bands at charge neutrality

Measured energy gaps between flat and dispersive bands

Observed a finite gap at zero electric field, suggesting interaction effects

Abstract

We experimentally investigate the band structures of chirally twisted triple bilayer graphene. The new kind of moir\'e structure, formed by three pieces of helically stacked Bernal bilayer graphene, has flat bands at charge neutral point based on the continuum approximation. We experimentally confirm the existence of flat bands and directly acquire the gap in-between flat bands as well as between the flat bands and dispersive bands from the capacitance measurements. We discover a finite gap even at zero perpendicular electric field, possibly induced by the Coulomb interaction and ferromagnetism. Our quantitative study not only provides solid evidence for the flat-band and interesting physics, but also introduces a quantitative approach to explore phenomena of similar moir\'e systems.