Superconducting Dome in a Gate-Tuned Band Insulator

A dome-shaped superconducting region appears in the phase diagrams of many unconventional superconductors. In doped band insulators, however, reaching optimal superconductivity by the fine-tuning of carriers has seldom been seen. We report the observation of a superconducting dome in the temperature–carrier density phase diagram of MoS2, an archetypal band insulator. By quasi-continuous electrostatic carrier doping achieved through a combination of liquid and solid gating, we revealed a large enhancement in the transition temperatureTc occurring at optimal doping in the chemically inaccessible low–carrier density regime. This observation indicates that the superconducting dome may arise even in doped band insulators.