Highly Compressed Miassite Rh17S15: A Bose–Einstein Condensate Superconductor?

Miassite (rhodium sulfide Rh17S15) is the mineral with the highest superconducting transition temperature Tc = 5.5 K among other minerals. Laboratory-grown Rh17S15 phase has been studied by several groups, but the superconductivity in Rh17S15 is still not fully understood. Recently, Xu et al. [10] reported that the Tc in Rh17S15 at pressure range 2.5 GPa < P < 60 GPa is suppressed below 2.5 K. However, at pressure above P > 60 GPa the superconducting state reentrants and the highest transition temperature of Tc = 5 K was observed at P = 117.7 GPa. Here, the reported experimental temperature and magnetic field dependences of the resistance R(T, P, B) in highly compressed Rh17S15 were analyzed. As a result, I found that the ratio of the superconducting transition temperature, Tc, to the Fermi temperature, TF, in Rh17S15 at P = 110 GPa is Tc/TF = 0.150–0.167 that is surprisingly close to the Bose–Einstein condensate ratio Tc/TF = 0.176.