  Many recent studies show that superconductivity not only exists in atomically
thin monolayers but can exhibit enhanced properties such as higher transition
temperature and stronger critical field. Nevertheless, besides being air
unstable, weak tunability in these intrinsically metallic monolayers has posed
a severe limitation in exploring monolayer superconductivity, hence hindering
possible applications in electronic devices. Using field effect gating, we
prepared monolayer superconductivity in easily accessible CVD-grown WS2, a
typical ambient stable semiconducting transition metal dichalcogenide (TMD).
Here, we present a complete set of competitive electronic phases over an
unprecedented range from band insulator, superconductor, to an unexpected
re-entrant insulator. Throughout the superconducting dome, the Cooper pair spin
is pinned by a strong internal spin-orbit interaction, making this material
arguably the most resilient superconductor in a magnetic field. The re-entrant
insulating state at positive high gating voltages is plausibly attributed to
localization induced by the characteristically weak screening of the monolayer,
providing the key insight into many dome-like superconducting phases observed
in field induced quasi-2D superconductors.
