Probing the nature of an emergent insulator in ionic gated monolayer transition metal dichalcogenides

Abstract

Electronic correlation in a flat band has been a longstanding interest because of emergent phenomena such as Mott insulator and superconductivity. Besides recent Moiré superlattice, transition metal dichalcogenides (TMDs) may directly, e.g. by forming a charge density wave in 1T-TaS2, reconstruct a narrow band that exhibits a correlated insulator. Here we report an emergent insulator in electron doped monolayer WSe2, a prototypical TMDs with direct bandgaps. By detailed mapping a cascade of phases “band insulator-superconductor-emergent insulator-metal”, we can identify, besides the superconducting dome, a narrow miniband split from the conduction band, half filling of which coincides with the insulating state. The correlation picture is supported by a density wave that possesses an isolated flat band. Finally, through evolutionary changes within the same class of materials, multivalley population is suggested to account for enhanced superconductivity and the insulator. Our finding provides new opportunities to explore correlated physics within traditionally non-correlated materials.

Anomalous Metallic Phase in Molybdenum Disulphide Induced via Gate-Driven Organic Ion Intercalation

“…A first source of localization could be the randomness caused by intercalation and progressive introduction of disorder in the form of extra scattering centers due to the presence of the ions themselves [36,[83][84][85][86][87]: this type of gate-driven re-entrant transition (from a band insulator, to a metal, and finally to an Anderson insulator) has already been reported in other ion-gated TMDs [88][89][90] and oxides [42]. A second source of localization could instead be associated to the same phenomenon giving rise to the resistivity anomaly, which is often found among TMDs and represents one of the typical signatures of the onset of CDW phases [1].…”

“…A first source of localization could be the randomness caused by intercalation and progressive introduction of disorder in the form of extra scattering centres due to the presence of the ions themselves [ 36 , 83 , 84 , 85 , 86 , 87 ]: this type of gate-driven re-entrant transition (from a band insulator, to a metal and finally to an Anderson insulator) has already been reported in other ion-gated TMDs [ 88 , 89 , 90 ] and oxides [ 42 ].…”