Abnormal Normal State and Pressure-driven Reentrant Superconductivity in the Heavy $d$-electron Superconductor Rh$_{17}$S$_{15}$

TL;DR

This study reveals that Rh$_{17}$S$_{15}$ exhibits a ferromagnetic normal state and pressure-induced reentrant superconductivity, suggesting unconventional superconductivity driven by complex magnetic interactions.

Contribution

It uncovers the coexistence of ferromagnetism and superconductivity in Rh$_{17}$S$_{15}$ and demonstrates pressure-driven reentrant superconductivity with a higher critical temperature.

Findings

Normal state exhibits weak ferromagnetism up to room temperature.

Superconductivity is suppressed by pressure and reemerges at higher pressures with increased T_c.

Evidence suggests unconventional superconductivity in Rh$_{17}$S$_{15}$.

Abstract

Superconductivity beyond the conventional Bardeen-Cooper-Schrieffer (BCS) framework often emerges out of a normal state that is accompanied by exotic magnetism and thereby displays many exceptional transport and thermodynamic properties. Here we report that the normal state of the heavy $d$-electron superconductor Rh$_{17}$S$_{15}$ is characterized by a weak \textit{ferromagnetism} that persists up to room temperature. We show that the broad hump in its resistivity likely results from the Kondo interaction of the conduction electrons with this novel magnetism. By applying pressure, superconductivity is fully suppressed first. In the high-pressure regime, however, we observe a second dome of superconductivity with its maximum $T_c$ greater than the ambient pressure value, highlighting the possible \textit{unconventional} superconductivity in this heavy $d$-electron sulfide.