Graphite offers up new quantum surprise

Researchers at The University of Manchester in the UK, led by Dr. Artem Mishchenko, Prof Volodya Fal'ko and Prof Andre Geim, have discovered the quantum Hall effect in bulk graphite—a layered crystal consisting of stacked graphene layers. This is an unexpected result because the quantum Hall effect is possible only in so-called two-dimensional (2-D) systems where electrons' motion is restricted to a plane and must be disallowed in the perpendicular direction. They have also found that the material behaves differently depending on whether it contains odd or even number of graphene layers—even when the number of layers in the crystal exceeds hundreds. The work is an important step to the understanding of the fundamental properties of graphite, which have often been misunderstood, especially in recent years.