Gate-Controlled Potassium Intercalation and Superconductivity in Molybdenum Disulfide.

Abstract

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 <i>in</i> <i>situ</i> probe of dynamics of ion diffusion, carrier doping, and transport properties. Here we performed <i>in</i> <i>situ</i> 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.