Interplay of electronic crystals with integer and fractional Chern insulators in moir\'e pentalayer graphene

TL;DR

This paper explores how electronic crystals interact with integer and fractional Chern insulators in moiré pentalayer graphene, revealing tunable topological states and fractional Chern insulators driven by electron correlations.

Contribution

It demonstrates the emergence of tunable Chern insulators and fractional states in moiré pentalayer graphene, highlighting the interplay between electronic crystallization and topological phenomena.

Findings

Correlated insulators with tunable Chern number observed.

Evidence of fractional Chern insulators near specific fillings.

Multiple electronic crystal states that break translational symmetry.

Abstract

The rapid development of moir\'e quantum matter has recently led to the remarkable discovery of the fractional quantum anomalous Hall effect, and sparked predictions of other novel correlation-driven topological states. Here, we investigate the interplay of electronic crystals with integer and fractional Chern insulators in a moir\'e lattice of rhomobohedral pentalayer graphene (RPG) aligned with hexagonal boron nitride. At a doping of one electron per moir\'e unit cell, we see a correlated insulator with a Chern number that can be tuned between $C=0$ and $+1$ by an electric displacement field, accompanied by an array of other such insulators formed at fractional band fillings, $\nu$. Collectively, these states likely correspond to trivial and topological electronic crystals, some of which spontaneously break the discrete translational symmetry of the moir\'e lattice. Upon applying a modest magnetic field, a narrow region forms around $\nu=2/3$ in which transport measurements imply the emergence of a fractional Chern insulator, along with hints of weaker states at other fractional $\nu$. In the same sample, we also see a unique sequence of incipient Chern insulators arising over a broad range of incommensurate band filling near two holes per moir\'e unit cell. Our results establish moir\'e RPG as a fertile platform for studying the competition and potential intertwining of electronic crystallization and topological charge fractionalization.