Supermetallic conductivity in bromine-intercalated graphite

Abstract

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 $\ensuremath{\sim}6\text{ }\text{at}\text{ }\mathrm{%}$ 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 $(\ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}{10}^{4}\text{ }{\text{cm}}^{2}/\text{V}\ensuremath{\cdot}\text{s})$ 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.