Gate-Controlled Potassium Intercalation and Superconductivity in Molybdenum Disulfide

Intercalation of guest ions into a van der Waals (vdW) gap in layered materials is a powerful route to create novel material phases and functionalities. Ionic gating is a technique to control the motions and configuration of ions for both intercalation and surface electrostatic doping. The advance of ionic gating enables the in situ probe of dynamics of ion diffusion, carrier doping, and transport properties. Here we performed in situ resistivity and Raman experiments on the potassium ion (K⁺) intercalation of single-crystal MoS₂ and constructed a temperature-carrier density phase diagram. The K⁺-intercalation induces a structural transition from the prismatically coordinated phase to the octahedrally coordinated phase, where anisotropic three-dimensional superconductivity and a possible charge density wave state were observed. The present ionic gating offers a comprehensive view of the intercalated phases and proves that the electrostatically induced superconductivity is distinct from that in the intercalated phase.