Tuning of carrier concentration and superconductivity in high-entropy-alloy-type metal telluride (AgSnPbBi)(1-x)/4InxTe

High-entropy-alloy-type (HEA-type) compound superconductors have been drawing much attention as a new class of exotic superconductors with local structural inhomogeneity. (Ag,In,Sn,Pb,Bi)Te with a NaCl-type structure is a typical HEA-type superconductor, but the carrier doping mechanism had been unclear. In this study, we synthesized (Ag,In,Sn,Pb,Bi)Te polycrystalline samples with various In concentration using high-pressure synthesis; the chemical formula of the studied system is (AgSnPbBi)(1-x)/4InxTe (x = 0–0.4). Single-phase samples were obtained for x = 0–0.3. A semiconductor-like temperature dependence of resistivity was observed for x = 0, while metallic behavior and superconductivity appeared for the In-doped samples. The highest transition temperature was 3.0 K for x = 0.3. The Seebeck coefficient decreases with increasing x, which suggests that In3+ generates electron carriers in (AgSnPbBi)(1-x)/4InxTe. Tuning of carrier concentration and superconducting properties of (Ag,In,Sn,Pb,Bi)Te would be useful for further investigation on exotic superconductivity in the HEA-type compound.