Field-Induced Superconductivity in MoS2

Semiconducting TMDs are nowadays attracting great interest after the invention of the so-called "Scotch-tape method" established in graphene research. Semiconducting TMDs are front-runners of "post graphene" materials for their finite band gap crucial for device applications. MoS2 is the most widely used TMD because of its application as a solid lubricant. Scientifically, it shows superconductivity after alkali or alkaline-earth doping with a highest T (c) of around 7 K. Recently, we succeeded in inducing superconductivity in the MoS2 transistor adopting electric double layer (EDL), a nanosized capacitor, as a gate dielectric. The field-induced superconducting transition of MoS2 was realized with a maximum T (c) around 11 K, the highest not only within a reported MoS2 compound, but also among TMDs. This highest T (c) lies in the carrier density region much smaller than a chemically doped compound; a low density region has never been successfully accessed by chemical methods. Combining a HfO2 (high-k) back gate, quasi-continuous control of carrier density, and thus quantum phase, was demonstrated to unveil the phase diagram; the T (c) exhibits strong carrier density dependence with a superconducting dome. Our result implies a common existence of the superconducting dome in 2D band insulators.