Layers of a thin material rotated relative to each other resemble stacked grids. Where the lines intersect, a new pattern emerges — a moiré. In this pattern, electrons move differently than in a regular crystal and can form unexpected states.
In the new study, researchers took two layers of molybdenum telluride and twisted them by 4.8 degrees. Using an electric field, they tuned the material so that electrons filled special points where their energy sharply increases. At these points, electron interactions are enhanced, and the material spontaneously acquired magnetic properties. Measurements showed that this is not just magnetization: electrons from different "valleys" (regions in momentum space) aligned into a coherent antiferromagnetic order. Adding electrons slightly tilted this order, and a magnetic field transformed it into a vortex-like structure that produces an additional electrical signal.
With a further increase in the magnetic field, the material transitioned into a state where electric current flows only along the edges, while the interior is insulating. This state has nontrivial topology and can be switched on and off with an electric field. Such control over magnetic and topological properties paves the way for new types of electronics where information is stored and processed without losses.
A moiré pattern arises when two identical periodic patterns are overlaid with a slight rotation — for example, two window screens. In twisted materials, this pattern alters electron properties so strongly that the material can become a superconductor or a magnet.