Spontaneous Electric Polarization in Graphene Polytypes

Abstract

AbstractSpontaneous electric polarization is recently observed in multilayered van der Waals stacked materials, arising from a symmetry breaking in a unit cell with two or more constituent species, or non‐centrosymmetric intra‐layer atom displacement in single‐atom‐species materials. Here, it is shown that even elemental crystals, consisting of one type of atom and composed of non‐polar and centrosymmetric layers, exhibit electric polarization if arranged in an appropriate three‐dimensional  architecture. This concept is demonstrated here for mixed‐stacking tetra‐layer polytypes of non‐polar graphene sheets. Surprisingly, it is find that the room temperature out‐of‐plane electric polarization increases with external electrostatic hole doping, rather than decreases with it owing to screening. Using first‐principles calculations, as well as a self‐consistent tight‐binding model, the emergence of polarization is explain in terms of inter‐layer charge rearrangement and the doping dependence in terms of gating‐induced inter‐layer charge transfer. This newly discovered intrinsic polarization may therefore offer new venues for designing the electronic response of graphene‐based polytypes to external fields.