Physicists create traps for electrons in graphene

Scientists have studied the properties of two-layer graphene, the sheets of which are rotated relative to each other and unevenly stretched. It turned out that this creates regions with different densities of electronic states. The research is published in the journal Physical Review Letters.

A hexagonal carbon material just one atom thick – graphene – has attracted the attention of physicists in recent years due to a number of unique properties. One of them is the exceptional conductivity of this substance, in which electrons are effectively massless particles. However, for many applications it is necessary to create materials with different electronic properties. It turns out that graphene alone with small changes can be sufficient in many cases.

Scientists have recently shown that bilayer graphene has superconducting properties if its layers are rotated at a certain angle. The new work shows that the electronic properties can be controlled over a wider range. Vincent Renard and his colleagues at the University of Grenoble-Alpes synthesized bilayer graphene, the layers of which were unevenly stretched. As a result, in addition to the periodicity of the crystal lattice inside the layers, all matter began to have periodicity on a larger scale: in some regions, atoms of different layers were located one above the other, and in others, spaced at a strictly defined distance, they were located opposite the center of the hexagonal cells of the second layer.

As a result, the electronic properties have changed dramatically, which was experimentally demonstrated using measurements on a scanning tunneling microscope. The experiments showed that in the places where the lattices coincided, a significantly increased number of electronic states was observed, while in the regions where the lattices were mismatched by half a period, there were much fewer such states, that is, the electrons avoided them. At the moment, such a structure does not provide specific advantages over other approaches to the use of graphene, but the authors hope that their work will become the beginning of a new approach, and theoretical work will make it possible to predict structures with

the desired properties.