Superconductivity in Ti0.6Bi2Te3 Derived from a Topological Insulator

Bulk superconductivity has been discovered in Tl0.6Bi2Te3, which is derived from the topological insulator Bi2Te3. A superconducting volume fraction of up to 95% (determined from the specific heat) with a T-c of 2.28 K was observed. The carriers are p-type with a density of similar to 1.8 X 10(20) cm(-3). Resistive transitions under magnetic fields point to an unconventional temperature dependence of the upper critical field B-c2. The crystal structure appears to be unchanged from that of Bi2Te3, with a shorter c lattice parameter, which, together with the Rietveld analysis, suggests that Tl ions are incorporated but not intercalated. This material is an interesting candidate for a topological superconductor that may be realized by the strong spin-orbit coupling inherent to topological insulators.