  It is demonstrated that both transmission and reflection coefficients
associated to the Klein paradox at a step barrier are positive and less than
unity, so that the particle-antiparticle pair creation mechanism commonly
linked to this phenomenon is not necessary. Because graphene is a solid-state
testing ground for quantum electrodynamics phenomena involving massless Dirac
fermions we suggest that the transport characteristic through a p-n graphene
junction can decide between the results obtained in this paper and the common
Klein paradox theory, which imply negative transmission and higher-than-unity
reflection coefficients. Recent experimental evidence supports our findings.

Quantum Physics