Moiré effect: How to twist material properties

© Erik Zumalt, Lukas Linhart - 2D materials have triggered a boom in materials research. Now it turns out that exciting effects occur when two such layered materials are stacked and slightly twisted. The discovery of the material graphene, which consists of only one layer of carbon atoms, was the starting signal for a global race: Today, so-called "2D materials" are produced, made of different types of atoms. Atomically thin layers that often have very special material properties not found in conventional, thicker materials. Now another chapter is being added to this field of research: If two such 2D layers are stacked at the right angle, even more new possibilities arise. The way in which the atoms of the two layers interact creates intricate geometric patterns, and these patterns have a decisive impact on the material properties, as a research team from TU Wien and the University of Texas (Austin) has now been able to show. Phonons - the lattice vibrations of the atoms - are significantly influenced by the angle at which the two material layers are placed on top of each other.