Electrical switching of Chern insulators in moire rhombohedral heptalayer graphene

Abstract

In orbital Chern insulators, the chemical potential acts as a tuning knob to reverse chirality in dissipationless edge currents, enabling electric-field control of magnetic order-key for future quantum electronics. Despite the rise of orbital Chern insulators, electrically switchable quantum anomalous Hall effect (QAHE) remains rare, necessitating further investigation. Here, we demonstrate electric-field-induced reversal of orbital Chern insulators in a moire superlattice composed of rhombohedral heptalayer graphene (r-7LG) aligned with hexagonal boron nitride. At one electron per moire unit cell, two emerging Chern insulating phases - one pointing away from and the other toward graphene's charge neutrality point in the phase diagram of carrier density (n) versus magnetic field (B) - exhibit energetic competition modulated by both n and B. This switchable QAHE chirality in r-7LG demonstrates a layer-number dependent response: similar phenomena in moire r-6LG require much higher magnetic fields and are absent in thinner rhombohedral graphene. Our findings establish moire-engineered rhombohedral graphene as a promising platform for exploring topological quantum materials with electrically controllable chiral edge modes and magnetic order.