Nematic Superconductivity in Nodal Line Semimetal SnTaS2

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Abstract Nematic superconductivity spontaneously breaks the rotational symmetry and can host unconventional superconducting phases. Here, we report evidence of intrinsic nematic superconductivity in the nodal-line semimetal SnTaS2, a centrosymmetric layered material with hexagonal symmetry. Transport measurements on exfoliated nanoflakes reveal pronounced twofold in-plane anisotropy in the upper critical field, resistance, and critical current, in contrast to the sixfold lattice symmetry. The anisotropy strength increases with decreasing sample thickness, pointing to a surface-dominated origin, while the variation of the nematic orientation among different devices suggests that the nematic director is weakly pinned. Tunneling spectroscopy on SnTaS2–AlOx–Au junctions further shows a twofold angular modulation of the superconducting gap under in-plane magnetic fields. These results support an unconventional nematic superconducting state associated with the topological surface states and distinct from bulk pairing, establishing SnTaS2 as a promising platform for studying the interplay between the band topology and symmetry-broken superconductivity.

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