Supermetallic conductivity in bromine-intercalated graphite

Exposure of highly oriented pyrolytic graphite to bromine vapor gives rise to in-plane charge conductivities which increase monotonically with intercalation time toward values for 6 at % Br that are significantly higher than Cu at temperatures down to 5 K. Magnetotransport, optical reflectivity and magnetic susceptibility measurements confirm that the Br dopes the graphene sheets with holes while simultaneously increasing the interplanar separation. The high-room-temperature mobility 5 104 cm2 /V·s and resistance anisotropy together with the reduced diamagnetic susceptibility of the intercalated samples suggests that the observed supermetallic conductivity derives from a parallel combination of weakly coupled hole-doped graphene sheets.