This visualization shows the interaction of infrared light with double-layer graph. The interaction is created by special electron flows.
Graphene is one of the most fascinating materials in physics and materials science. It consists of a grid of carbon atoms only one atomic layer thick, the hexagonal arrangement of which resembles the pattern of a chain link fence. If you combine two of these layers and twist them at a certain angle, interactions arise that can even tame light.
These special optical properties of the double-layer graph were already suspected in theory, but could never be proven in experiments. A team led by the Barcelona Institute of Science and Technology has now succeeded for the first time. To do this, the scientists irradiated the graphene with infrared light and examined the reaction of the material on the order of 20 nanometers.
So-called plasmons are decisive for the electromagnetic interactions in graphs. These are quantized waves of electrons that appear in the twisted double-layer graph and are amplified by a kind of moiré effect. This effect comes from the repeating structures of the carbon lattice and ensures varying electron densities within the material.
The plasmons can interact with and guide infrared light. The currents depend on the local structure of the graph and could therefore be used in a targeted manner. The scientists therefore see their research as the basis for future analytical methods. Gas and biomolecules could be detected optically with the help of the plasmons.