Superconductivity in Intercalated Molybdenum Disulfide

Superconductivity has been observed in the Na, K, and Rb intercalates of molybdenum disulfide (${\mathrm{MoS}}_2$ ). The superconducting transitions are wide (several degrees) and not complete down to the lowest temperature studied (∼.6°K). The onset of superconductivity ranged from ∼6.5°K for the potassium and rubidium compounds to ∼4,5° K for the sodium compounds. A two phase type of transition was observed only for the potassium intercalated compounds. An x‐ray analysis of these systems indicated: (1) Partial intercalation of some of the samples; (2) expansion of the unit cell upon intercalation, and (3) the possible existence of two different expansions in the potassium and sodium compounds. An investigation of the effect of crystal orientation on the superconducting transition is in progress.