Frustrated van der Waals heterostructures

Geometrical frustration results from the packing of constituents in a lattice, where the constituents have conflicting forces. The phenomenon is known in glass materials, and this work expands the concept of geometrical frustration into the realm of van der Waals two-dimensional materials. Using density functional theory with the r$^2$SCAN+rVV10 exchange-correlation potential, we find a number of two-dimensional heterostrutures with alternating strains, where one layer is strained and the adjacent layer is compressed. By comparing the thermodynamic stability of this class of materials, frustrated van der Waals heterostructures, with the non-frustrated counterparts, we report 9 frustrated materials that are more thermodynamically stable out of 14 examined structures. Frustration in 4 of the 14 van der Waals heterostructures were found to either increase or decrease the bandgap of the non-frustrated heterostructure. We discuss possible fabrication pathways for creating this class of materials.