Optimizing the superconducting transition temperature and upper critical field of Sn_1-xIn_xTe

Sn_1-xIn_xTe is a possible candidate for topological superconductivity. Previous work has shown that substitution of In for Sn in the topological crystalline insulator SnTe results in superconductivity, with the transition temperature, T_c, growing with In concentration. We have performed a systematic investigation of Sn_1-xIn_xTe for a broad range of x, synthesizing single crystals (by a modified floating-zone method) as well as polycrystalline samples. The samples have been characterized by x-ray diffraction, resistivity, and magnetization. For the single crystals, the maximum T_c is obtained at x=0.45 with a value of 4.5 K, as determined by the onset of diamagnetism.