Spin–orbit–parity coupled superconductivity in atomically thin 2M-WS2

The investigation of two-dimensional atomically thin superconductors—especially those hosting topological states—attracts growing interest in condensed-matter physics. Here we report the observation of spin–orbit–parity coupled superconducting state in centrosymmetric atomically thin 2M-WS 2 , a material that has been predicted to exhibit topological band inversions. Our magnetotransport measurements show that the in-plane upper critical field not only exceeds the Pauli paramagnetic limit but also exhibits a strongly anisotropic two-fold symmetry in response to the in-plane magnetic field direction. Furthermore, tunnelling spectroscopy measurements conducted under high in-plane magnetic fields reveal that the superconducting gap possesses an anisotropic magnetic response along different in-plane magnetic field directions, and it persists much above the Pauli limit. Self-consistent mean-field calculations show that this unusual behaviour originates from the strong spin–orbit–parity coupling arising from the topological band inversion in 2M-WS 2 , which effectively pins the spin of states near the topological band crossing and gives rise to an anisotropic renormalization of the effect of external Zeeman fields. Our results identify the unconventional superconductivity in atomically thin 2M-WS 2 , which serves as a promising platform for exploring the interplay between superconductivity, topology and strong spin–orbit–parity coupling. A form of superconductivity where strong spin–orbit coupling combines with topological band inversions to produce strong robustness against magnetic fields is shown in a few-layer transition metal dichalcogenide.