Nodal superconductivity in synthetic miassite

Dozens of elements in the periodic table superconduct at low temperatures. However, the elements are normally found as a component of naturally occurring minerals, making superconductivity in natural substances extremely rare. There are known mineral superconductors including covellite (CuS), parkerite (Ni₃Bi₂S₂), and miassite (Rh₁₇S₁₅). While superconductivity in the elemental superconductor is well-described by the conventional Bardeen-Cooper-Schrieffer (BCS) mechanism. The mineral superconductor may host non-BCS type superconductivity. We have studied the normal and superconducting properties of synthetic miassite via electrical transport and London penetration depth measurements with controlled disorder. In this talk, I will present the results of our experimental investigation and discuss possible nodal superconductivity which has been observed only in lab-discovered strongly correlated electronic systems such as heavy fermion compounds, high-T_c cuprates, and iron-pnictides. Our discovery implies that exotic nodal superconductivity may naturally occur.