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

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 ($\simeq 0.4H{}_{c2}$). 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.

7 pages, 6 figures