Superconductivity in quasi-one-dimensional BaNbS3

BaNbS3 is a quasi-one-dimensional metal possessing Nb-Nb chains. Superconductivity was observed at the transition temperature Tc = 0.89 K. Specific heat measurements reveal the bulk nature of the superconductivity, and an energy gap Eg = 0.245(3) meV, which agrees well with BCS theory. The upper critical magnetic field was used to estimate the coherence lengths parallel (ξ∥ = 987(17) Å) and perpendicular (ξ⊥ = 204(12) Å) to the Nb-Nb chains. Despite the anisotropy evident through ξ∥/ξ⊥, the large magnitudes of each reveal that coherence extends over a large enough volume that superconductivity in BaNbS3 can be viewed as isotropic on the scale of tens of Nb-Nb distances.