Ferroelectric Polarization in an h-BN-Encapsulated 30-Twisted Bilayer-Graphene Heterostructure

Recently, the emergent two-dimensional (2D) ferroelectric materials have provided new possibilities for the miniaturization of ferroelectric systems and the integration of novel 2D nano-electronic devices. In addition to the intrinsic ferroelectrics exfoliated from bulk, 2D heterostructures hybridized from electrically non-polarized van der Waals (vdW) materials have also been proven to be a promising platform for the construction of ferroelectricity. Here, we report 30 degrees twisted bilayer-graphene (TBLG) incommensurate moire superlattice encapsulated by hexagonal boron nitride (h-BN), in which robust hysteretic resistance was detected at the top interface between h-BN and the TBLG from room temperature down to 40 mK. The hysteretic phenomenon can be understood by the extra carrier induced by the interfacial 2D ferroelectric polarization, which is estimated to be around 0.7 pC/m. Our work of interfacial ferroelectric heterostructure achieved by a TBLG/h-BN hybrid system expands the 2D ferroelectric families and opens more possibilities for future coupling the ferroelectricity with rich electronic and optical properties in vdW twistronic devices.