Ferroelectric In2Se3-modulated polymorph recognition in tetralayer graphene

Precise characterization of tetralayer graphene (4LG) configurations is crucial for exploring their rich physical phenomena and applications. Existing methods struggle to distinguish configurations, especially degenerate polar ones, due to remarkable band differences only near the Fermi level. We present an approach using α-In2Se3/4LG van der Waals (vdW) heterostructures to enhance 4LG's features. First-principles calculations reveal that an α-In2Se3's polarization field modifies a 4LG's band structure, amplifying configurational differences and lifting degeneracies in polar structures. This enables better experimental identification of 4LG configurations and measurement of out-of-plane polarity. We demonstrate that this enhancement arises solely from the modulation of the intrinsic electric fields of 2D ferroelectric materials and interfacial charge transfer. In experiments, both methods—applying electric fields and charge doping—have been widely used to tune material properties, and some devices that utilize ferroelectric polarization fields to modulate performance have already been successfully fabricated. Therefore, we believe that 2D ferroelectric materials can act as “structural filters” for vdW multilayer materials, not limited to the 4LG discussed in this paper, providing a tool for distinguishing multilayer configurations. Our work expands 2D ferroelectrics' applications and provides insights for nanodevice design based on vdW heterostructures.