Pauli-limit violation and nodeless two-gap superconductivity in noncentrosymmetric ℎ-NbS single crystals

Here, the authors report the crystal and electronic structures, and superconductivity of $h$-NbS single crystals with site-selective Nb vacancies. This compound has a noncentrosymmetric lattice structure and exhibits Nb vacancy dependent electronic structure. $h$-NbS is a two-gap $s+s$-wave superconductor with a moderate coupling strength. The broken inversion symmetry leads to a Pauli limit violation in this three-dimensional superconductor with very low anisotropy. These findings highlight the interplay between crystal symmetry, dimensionality, stoichiometry, and superconductivity in transition metal chalcogenide superconductors.