Superconductivity in non-centrosymmetric rhombohedral NbSe₂

The transition-metal dichalcogenides (TMDs) host superconductivity across distinct polytypes with contrasting crystal symmetries and spin–orbit coupling (SOC) textures. Here we synthesize rhombohedral-stacked NbSe₂ (3R-NbSe₂) single crystals and establish their superconductivity in bulk and few-layer flakes. The superconducting transition temperature T_C shows a linear scaling with the residual resistivity ratio (RRR) for RRR < 5, while shows no systematic dependence on thickness. The contrasting behavior compared to 2H phase indicates mixed-parity pairing enabled by inversion-symmetry breaking and antisymmetric SOC (ASOC) in rhombohedral stacking. In bulk and thin-layer 3R-NbSe₂, the in-plane upper critical field H_c2 exceeds the Pauli limit, suggesting that the out-of-plane Ising-like SOC component remains effective in suppressing Zeeman pair breaking. For thin layers, the suppression of orbital depairing enhances Pauli limiting and the additional Rashba-type SOC allowed by broken inversion symmetry may enable finite-momentum pairing, consistent with FFLO-like transport signatures observed down to a pentalayer flake. Our results identify 3R-NbSe₂ as a minimal, single-phase non-centrosymmetric superconductor where disorder acts as an efficient tuning knob and provide a platform to explore Pauli-limit violation, parity-mixed pairing, and possible nonreciprocal transport phenomena in TMDs superconductors.