This Demonstration shows the tunneling through a barrier of height and width by a Dirac fermion of mass and energy . The upper two Argand plots show the weight of the reflected and transmitted waves (red: , green: , and blue: ). The lower plot shows the reflection coefficient (blue) and transmission coefficient (red). The gray area is where . The increase in the transmitted wave after tunneling is a consequence of the Klein paradox.
This Demonstration implements the reflection from a barrier for a Dirac electron. For further details, see
 R.–K. Su, G. G. Siu, and X. Chou, "Barrier Penetration and the Klein Paradox," Journal of Physics A: Mathematical and General, 26, 1993 pp. 1001–1005.
 M. I. Katsnelson, K. S. Novoselov, and A. K. Geim, "Chiral Tunnelling and the Klein Paradox in Graphene," Nature Physics, 2, 2006 pp. 620–625.