Superconductivity in In-doped AgSnBiTe with possible band inversion.

We investigated the chemical pressure effects on structural and electronic properties of SnTe-based material using partial substitution of Sn by AgBi, which results in lattice shrinkage. For Sn(AgBi)Te, single-phase polycrystalline samples were obtained with a wide range of x. On the basis of band calculations, we confirmed that the Sn(AgBi)Te system is basically possessing band inversion and topologically preserved electronic states. To explore new superconducting phases related to the topological electronic states, we investigated the In-doping effects on structural and superconducting properties for x = 0.33 (AgSnBiTe). For (AgSnBi)InTe, single-phase polycrystalline samples were obtained for y = 0-0.5 by high-pressure synthesis. Superconductivity was observed for y = 0.2-0.5. For y = 0.4, the transition temperature estimated from zero-resistivity state was 2.4 K, and the specific heat investigation confirmed the emergence of bulk superconductivity. Because the presence of band inversion was theoretically predicted, and the parameters obtained from specific heat analyses were comparable to In-doped SnTe, we expect that the (AgSnBi)InTe and other (Ag, In, Sn, Bi)Te phases are candidate systems for studying topological superconductivity.