Graphene – a single atom-thick layer of graphite – is an amazing laboratory for studying what would usually be thought of as relativistic effects. Its charge carriers have velocities that do not depend on their energies, rather like photons, which always move at the velocity of light. If you think of the carriers as massless, charged fermions in two dimensions and you work out the well known Landau levels that occur in a magnetic field, theory predicts something quite different from the usual states observed for massive electrons.
Phillip First and colleagues at the Georgia Institute of Technology, Atlanta, and the National Institute of Standards and Technology have managed to measure these Landau levels. They have found the predicted unequal energy levels, including a zero energy state, where the material has no electrical carriers until a magnetic field has been applied.
Further reading
D L Miller 2009 Science 324 924.