Superconductivity in Tl0.6Bi2Te3 Derived from a Topological Insulator

Bulk superconductivity has been discovered in Tl 0.6 Bi 2 Te 3, which is derived from the topological insulator Bi 2 Te 3 . 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 ∼1.8 × 10 20 cm –3 . Resistive transitions under magnetic fields point to an unconventional temperature dependence of the upper critical field B c 2 . The crystal structure appears to be unchanged from that of Bi 2 Te 3, 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.