Gate-Controlled\nPotassium Intercalation and Superconductivity\nin Molybdenum Disulfide

Intercalation of guest ions into\na van der Waals (vdW) gap in layered\nmaterials is a powerful route to create novel material phases and\nfunctionalities. Ionic gating is a technique to control the motions\nand configuration of ions for both intercalation and surface electrostatic\ndoping. The advance of ionic gating enables the <i>in</i> <i>situ</i> probe of dynamics of ion diffusion, carrier\ndoping, and transport properties. Here we performed <i>in</i> <i>situ</i> resistivity and Raman experiments on the potassium\nion (K<sup>+</sup>) intercalation of single-crystal MoS<sub>2</sub> and constructed a temperature–carrier density phase diagram.\nThe K<sup>+</sup>-intercalation induces a structural transition from\nthe prismatically coordinated phase to the octahedrally coordinated\nphase, where anisotropic three-dimensional superconductivity and a\npossible charge density wave state were observed. The present ionic\ngating offers a comprehensive view of the intercalated phases and\nproves that the electrostatically induced superconductivity is distinct\nfrom that in the intercalated phase.