Effects of impurities in two-dimensional graphite

The impurity effects in a two-dimensional graphite sheet (graphene) are studied by self-consistent T-matrix approximation. Conductivity is found to be modestly enhanced from a universal value 4e(2)/(pi h(2)), where -e is the electron charge and h is the Planck constant, by strong long-range potential. The staggered susceptibility of pi electrons is enhanced by strong impurity scattering irrespective of its range; it logarithmically diverges as T -> 0 in the unitarity limit.