Electric-Field-Induced Insulator-to-Metal and Superconducting Transitions in Bulk Polycrystalline MoS2: Role of the Gate Electrode Configuration

Layered transition metal dichalcogenides, such as MoS2, are promising platforms for exploring electric-field-controlled phenomena. While gate-induced superconductivity has been extensively studied in single-crystalline MoS2 flakes, the behavior of bulk polycrystalline MoS2 under similar conditions remains unexplored. In this study, we investigate electric-field-induced phase transitions in bulk polycrystalline MoS2 using an ionic liquid (IL) gate, focusing on the role of electrode configuration and contact proximity in transport properties, and on the emergence of superconductivity in bulk samples. Three different electrode configurations were employed to examine the impact of contact geometry. In setups with distant contacts, the samples exhibited insulating behavior down to 1.8 K, whereas in the configuration with contacts placed close to the gate electrode, a clear metal–insulator transition and the onset of superconductivity were observed, with a maximum Tc of 4.2 K. Analysis revealed that the contact resistance strongly depends on the distance between the gate electrode and the voltage/current leads, differing by nearly an order of magnitude between contacts located near and far from the gate. The critical apparent sheet resistance at the metal–insulator transition was estimated to be ~ 50 Ω, much lower than the quantum resistance, likely due to penetration of the IL into the granular polycrystalline structure. These findings highlight the crucial role of electrode configuration in IL gating of bulk materials and demonstrate that electrostatic doping can induce superconductivity in polycrystalline systems, extending the scope of gate-controlled quantum phenomena to materials for which high-quality single crystals are difficult to obtain.