Across‐Layer Sliding Ferroelectricity in 2D Heterolayers

Abstract Although the monolayers of most 2D materials are non‐ferroelectric with highly symmetric lattices, symmetry breaking may take place in their bilayers upon some stacking configuration, giving rise to so‐called sliding ferroelectricity where the vertical polarizations can be electrically reversed via interlayer translation. However, it is not supposed to appear in systems like graphene bilayer with centro‐symmetry at any stacking configuration, and the origin of the recently reported ferroelectricity (Nature 2020, 588, 71) in graphene bilayer intercalated between h‐BN remains mysterious. Here, a type of across‐layer sliding ferroelectricity that arises from the asymmetry of next‐neighbor interlayer couplings is proposed. The first‐principles evidence is shown that the vertical polarizations in intercalated centro‐symmetric 2D materials like graphene bilayer can be switched via multilayer sliding, which is likely to be the origin of the observed ferroelectric hysteresis. Moreover, such ferroelectricity may exist in a series of other heterolayers with quasi‐degenerate polar states, like graphene bilayer or trilayer on BN substrate, or even with a molecule layer on surface where each molecule can store 1‐bit data independently, resolving the bottleneck issue of sliding ferroelectricity for high‐density data storage.