  Bi2Se3 is one of a handful of known topological insulators. Here we show that
copper intercalation in the van der Waals gaps between the Bi2Se3 layers,
yielding an electron concentration of ~ 2 x 10^20cm-3, results in
superconductivity at 3.8 K in CuxBi2Se3 for x between 0.12 and 0.15. This
demonstrates that Cooper pairing is possible in Bi2Se3 at accessible
temperatures, with implications for study of the physics of topological
insulators and potential devices.
