Graphene: New bridge between condensed matter physics and quantum electrodynamics

Graphene is the first example of truly two-dimensional crystals-it is just one layer of carbon atoms. It turns out to be a gapless semiconductor with unique electronic properties resulting from the fact that charge carriers in graphene demonstrate charge-conjugation symmetry between electrons and holes and possess an internal degree of freedom similar to "chirality" for ultrarelativistic elementary particles. It provides an unexpected bridge between condensed matter physics and quantum electrodynamics (QED). In particular, the relativistic Zitterbewegung leads to the minimum conductivity of the order of conductance quantum e(2) / h in the limit of zero doping; the concept of Klein paradox (tunneling of relativistic particles) provides an essential insight into electron propagation through potential barriers; vacuum polarization around charge impurities is essential for understanding of high electron mobility in graphene; an index theorem explains the anomalous quantum Hall effect. (c) 2007 Elsevier Ltd. All rights reserved.