Transport and magnetic properties of Cr-, Fe-, Cu-doped topological insulators

We report a new class of three-dimensional topological insulators of transition metal doped Bi2Se3, TrxBi2Se3, and Bi2-xTrxSe3 (Tr Cr, Fe, Cu) with x = 0.15, for the intercalation and substitution cases. With varying the doping atoms, a great variety of properties are observed in a single crystal form. The Cu-intercalated crystal shows superconducting behavior below 3 K, where the diamagnetic signal is found. The increase of carrier density at low temperature is likely to be responsible for the superconductivity. The magnetically doped case of the Fe-substituted Bi2Se3 exhibits dominance of ferromagnetic interactions, whereas the Cr-substituted Bi2Se3 favors antiferromagnetic interactions. From these results, we learn that the peculiar transport and magnetic properties of topological insulator Bi2Se3 are easily tunable by chemical doping elements, which change the Fermi energy and manipulate the charge carriers. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549553]