On the superconducting gap structure of the miassite Rh17S15: Nodal or nodeless?

TL;DR

This study investigates the superconducting gap structure of Rh17S15, combining thermal conductivity measurements and first-principles calculations, revealing evidence for multigap nodeless superconductivity contrary to previous claims of nodal behavior.

Contribution

The paper provides the first thermal conductivity measurements down to 110 mK and uses electronic structure calculations to demonstrate multigap nodeless superconductivity in Rh17S15.

Findings

Negligible residual linear term in thermal conductivity suggests nodeless gaps.

Field dependence indicates multiple gaps with different magnitudes.

Electronic structure shows complex Fermi surfaces supporting multiband superconductivity.

Abstract

Recent penetration depth measurement claimed the observation of unconventional superconductivity in the miassite Rh$_{17}$S$_{15}$ single crystals, evidenced by the linear-in-temperature penetration depth at low temperatures, thereby arguing for the presence of the lines of node in its superconducting gap structure. Here we measure the thermal conductivity of Rh$_{17}$S$_{15}$ single crystals down to 110 mK and up to a field of 8 T ($\simeq 0.4H{\rm_{c2}}$). In marked contrast to the penetration depth measurement, we observe a negligible residual linear term $\kappa_0/T$ in zero field, in line with the nodeless gap structure. The field dependence of $\kappa_0(H)/T$ shows a profile that is more consistent with either a highly anisotropic gap structure or multiple nodeless gaps with significantly different magnitudes. Moreover, first-principles calculations give two electronic bands with complex shape of Fermi surfaces. These results suggest multigap nodeless superconductivity in this multiband Rh$_{17}$S$_{15}$ superconductor.