Energy Revolution: How Electricity Propagates in Graphene at the Speed of Light

Physicists observed electrons moving between two layers of carbon as if they had no mass, in a manner analogous to light.

These naturally occurring carbon layers represent the thinnest form of graphite and are known as "bilayer graphene" or "Bernal bilayer graphene." This name honors the scientist John Desmond Bernal [1901-1971], who studied the crystalline structure of substances. In Bernal stacking (or AB stacking), a carbon atom in the top layer sits directly above the center of a hexagon in the bottom layer, unlike AA stacking, where the atoms of the two layers align directly on top of each other. This type of AB stacking occurs naturally in graphite.

It was precisely in this Bernal stack that Anna Seiler and her colleagues at the University of Göttingen, in Germany, recorded electrons moving like photons, or particles of light, which have no mass. In addition to moving much faster, the electrons in the bilayer graphene exhibit the same scattering behavior as photons.

The most significant aspect is that the team demonstrated that this relativistic current can be switched on and off, paving the way for the development of tiny, energy-efficient, and ultrafast transistors. This is not possible in ordinary, single-layer graphene, as it lacks an insulating phase – graphene is an exceptional conductor of electricity and cannot be “switched off” to represent a “0” value in a transistor (it is always “on,” representing “1”).