Structural and Superconducting Properties of Bi2Rh3(Se1–xSx)2 (x = 0–1.0)

The structural and superconducting properties of the Bi-based superconductor Bi₂Rh₃(Se_1-xS_x)₂ were investigated over a wide pressure range. Bi₂Rh₃Se₂ is a superconductor with a superconducting transition temperature, T_c, of less than ∼1.0 K, whereas Bi₂Rh₃S₂ is a nonsuperconductor. The former shows a clear charge density wave (CDW) phase transition at 240 K and the latter shows a first-order structural phase transition at 165 K, providing the supercell structure. Both compounds have the same crystal structure at ambient temperature and pressure (monoclinic, space group of C2/m (No. 12)). This implies the possible formation of solid solution-like phases Bi₂Rh₃(Se_1-xS_x)₂. In this study, we prepared Bi₂Rh₃(Se_1-xS_x)₂ (x = 0-1.0) and investigated its superconducting properties and phase transitions at different x values. Because the superconducting properties and temperature causing the phase transition (T_pt) are quite different between Bi₂Rh₃Se₂ and Bi₂Rh₃S₂, their variation against x is quite intriguing from the viewpoint of the pursuit of physical properties via the replacement of Se with S. In this study, the features of the superconductivity and crystal structure against x were fully explored to depict the phase diagram. Moreover, we investigated the pressure (p) dependence of superconductivity and phase transition (CDW or the first-order structural transition) to clarify the interplay between the two ordered states.