Reversible electrical control of stacking order phase transition in few-layer graphene*

The layer stacking order has profound effects on physical properties of two-dimensional (2D) van der Waals heterostructures. For example, graphene multilayers can have distinct electronic band structures and behaviors depending on their stacking orders. Fascinating physical phenomena -- such as correlated insulators, superconductors, and ferromagnetism -- can also emerge with a periodic variation of the layer stacking order, known as the moiré superlattice in van der Waals materials. In this work, we demonstrate that a reversible phase transition between different layer stacking orders can be induced globally in few-layer graphene by electrostatic gating. We directly image the gate-induced stacking orders phase transition with infrared near-field optical microscopy. We reveal that both the carrier doping and the vertical electrical field can drive the stacking order phase transition, but with different mechanisms, through a systematic study of dual-gated few-layer graphene. Our findings provide a reversible and non-invasive method to globally control the stacking orders of few-layer graphene, and they have important implications for the understanding of gate-dependent quantum phenomena in graphene moiré superlattices.