Experiment finds graphene's missing pi Sep 14, 2007 Physicists
in the US claim to have solved the “mystery of the missing pi”,
which has confounded physicists studying graphene since the
material was discovered in 2004. The pi in question is related
to a discrepancy between the conductance of graphene as measured
in the lab and the value predicted by theory. The team measured
the conductance along tiny pieces of graphene as a function of
both an applied voltage and the ratio between the length and
width of the sheets. The results suggest that the theory is
correct -- but only for very small sheets with specific shapes
(Science 317 1530). Graphene is the darling of nanotechnologists
because it is tough, easy to make and a very good conductor of
both heat and electricity. The fact that it is one atom thick
also makes it an ideal system for exploring the often bizarre
properties of “two-dimensional” electrons. Perhaps the most
curious property of graphene is that it appears to behave like
both a metal and a semi