Bulk Superconductivity Induced by Se Substitution in Self-Doped BiCh2-Based Compound CeOBiS2−xSex.

We report the Se substitution effects on the crystal structure, superconducting properties, and valence states of self-doped BiCh₂-based compound CeOBiS_2−xSe_x. Polycrystalline CeOBiS_2−xSe_x samples with x = 0–1.0 were synthesized. For x = 0.4 and 0.6, bulk superconducting transitions with a large shielding volume fraction were observed in magnetic susceptibility measurements; the highest transition temperature (T_c) was 3.0 K for x = 0.6. A superconductivity phase diagram of CeOBiS_2−xSe_x was established based on T_c estimated from the electrical resistivity and magnetization measurements. The emergence of superconductivity in CeOBiS_2−xSe_x was explained with two essential parameters of in-plane chemical pressure and carrier concentration, which systematically changed with increasing Se concentration. [ABSTRACT FROM AUTHOR]