Nb Intercalated/Substituted Bismuth Selenide Superconductor

The compound (Nb_xBi₂Se₃) is reported to have ferromagnetic order coexistence with superconductivity. To study how superconductivity changes in Nb_xBi₂Se₃, we synthesized for x=0 to 1. The superconductivity appears in all compound except x=0 but no ferromagnetic behavior. This implies that the superconductivity is stable in various Nb-doping. This contrasts the behavior of Sr_xBi₂Se₃ of which superconductivity appears in very little amount of Sr intercalation. In increasing Nb(x), the structure gradually changes from Bi₂Se₃ to BiSe. BiSe structure is one of the infinite layer structures in Bi-Se compounds discussed for their structural stability in various Bi-Se ratio. We observed BiSe structure to be stable beyond x=0.3 indicating that the superconductivity is stable in BiSe and the possibility of new doping mechanism achieved in the material family.