Manipulating Superlattice Potentials and Quantum Confinement in Graphene via Moiré Ferroelectricity.

Two-dimensional (2D) moiré ferroelectricity has recently garnered significant attention as a bottom-up approach to realizing ferroelectrics via van der Waals assembly. Besides the interesting ferroelectricity, the periodic electric fields of 2D ferroelectricity offer unprecedented opportunities to modulate the electronic properties of adjacent 2D materials. However, direct local characterization of this effect, essential for a deep understanding and application of the moiré ferroelectricity, is still lacking. Here, we utilize twisted hexagonal boron nitride (t-hBN) as a moiré ferroelectric substrate to tune the electrical properties of its overlying graphene. Using scanning tunneling microscopy (STM), we demonstrate with nanoscale spatial resolution that the t-hBN moiré ferroelectricity generates periodic potential in graphene to confine massless Dirac fermions. Our experiment further indicates that we can reversibly alter the ferroelectric polarizations around the t-hBN moiré boundaries via the STM tip. This tunability of adjacent material properties opens new avenues for advanced heterostructures and devices based on 2D moiré ferroelectricity.