Research Highlights

For the better part of a decade, engineers have been crafting and testing recipes for so-called van der Waals heterostructures: stacks of atomically thin crystal layers that can be sequenced just so. Compared with a homostructure — the nanoscopic equivalent of a slab of ham — a heterostructure might feature slices of pastrami, pepperoni and pepper jack, all held together by the weak van der Waals forces among neighboring atomic layers.

Engineers soon discovered that the diversity could cultivate technologically interesting properties, often in the regions where two different materials meet, that are otherwise difficult or impossible to recreate. Then, a few years ago, researchers began exploring the effects of rotating the layers within van der Waals stacks. That misalignment of layers, they found, could also yield interesting results — turning a material into a superconductor, for instance, or changing how a semiconductor emits light.

Yet the achievement came in the face of a considerable challenge: Despite the weakness of van der Waals forces, adjacent layers strongly prefer to remain aligned. Manually stacking layers one by one can overcome the issue but demands extreme precision and, more importantly, time that large-scale manufacturers of small-scale technology just don’t have.