Superconducting gap structure of the miassite Rh17S15: Nodal or nodeless

Abstract

Recent penetration depth measurement reported the observation of possible unconventional superconductivity in the miassite Rh17S15 single crystals, evidenced by the linear-in-temperature penetration depth at low temperatures, thereby suggesting the presence of the lines of node in its superconducting gap structure. Here we measure the thermal conductivity of Rh17S15 single crystals down to ∼110 mK and up to a field of 8 T (≃0.4Hc2). In marked contrast to the penetration depth measurement, we observe a negligible residual linear term κ0/T in zero field, in line with the nodeless gap structure. The rapid increase of κ0(H)/T at low field suggests multiple nodeless gaps with significantly different magnitudes. The multigap structure is also supported by the specific heat data, which suggests one of the energy gaps is much smaller than the other. This small superconducting gap may help to reconcile two seemingly conflicting views on the superconducting gap structure, from the penetration depth and the thermal conductivity measurements. Finally, the first-principles calculations show two electronic bands crossing the Fermi level, forming a complex shape of Fermi surfaces. We discuss the implications of our findings for any possible unconventional superconductivity in this strongly correlated d-electron system.

Source-reported materials — not catalogue approval

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