A review article, ‘Klein Tunneling in Graphene: Optics with Massless Electrons,’ written by J.N. Fuchs and P.E. Allain of the Université Paris-Sud in the European Physical Journal, discusses the hypothetical and experimental findings to date on tunneling of electrons via energy barriers in one-carbon-atom-thick material called graphene.
Graphene is a good room temperature electrical conductor like copper and exhibits superior heat conductance compared to other materials. It is a nearly transparent material and its honeycomb lattice shape makes it very dense. Hence, it is ideal for light panel and touch screen applications.
Electrons moving within graphene like massless particles can explain the properties of the material. Their characteristics can be explained by the massless Dirac equation utilized for high-energy particles like neutrinos that have speed close to that of light. However, electrons are travelling inside graphene at a constant velocity 300 folds lesser than that of light.
In this article, the authors discuss the occurrence of tunneling effect during the transmittance of Dirac electrons present in graphene via various kinds of energy barriers in the material. In contrast to the laws of conventional mechanics, the tunneling of Dirac electrons of graphene occurs through its energy barriers irrespective of the barriers’ width and energy height. This phenomenon is known as Klein tunneling that was theoretically explained by Oskar Klein, a Swedish physicist, for three-dimensional massive Dirac electrons in 1929. Graphene was the first substance that demonstrated the Klein tunneling phenomenon experimentally, since large Dirac electrons needed large energy barriers for observation.