Chemical motifs in natural superlattice design

Many natural bulk systems crystallize in patterns of reduced dimensionality. For example, transition metal dichalcogenides (TMDs) consist of layered, two-dimensional structures. One way to modulate the structure and electronic properties of such a system is through an external, periodic potential. To this end, 2D heterostructures have been used to artificially engineer exotic electronic phases. Here, we discuss the development of natural superlattices, in which such heterostructures may be realized in a natural crystal. We describe the chemical relations that contribute to the stability of these structures, and we discuss how these are realized in recent TMD superlattice materials. We discuss how this translates to geometric relations in physical structures, which can aid in materials discovery of new types of superlattices in natural crystals.