Correlated insulator of excitons in WSe<sub>2</sub>/WS<sub>2</sub> moiré superlattices.

Xiong, Richen; Nie, Jacob H; Brantly, Samuel L; Hays, Patrick; Sailus, Renee; Watanabe, Kenji; Taniguchi, Takashi; Tongay, Sefaattin et al. · Science · 2023

basic_science · Level V

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Abstract

A panoply of unconventional electronic states has been observed in moiré superlattices. Engineering similar bosonic phases remains, however, largely unexplored. We report the observation of a bosonic correlated insulator in tungsten diselenide/tungsten disulfide (WSe<sub>2</sub>/WS<sub>2</sub>) moiré superlattices composed of excitons, that is, tightly bound electron-hole pairs. We develop a pump probe spectroscopy method that we use to observe an exciton incompressible state at exciton filling ν<sub>ex</sub> = 1 and charge neutrality, indicating a correlated insulator of excitons. With varying charge density, the bosonic correlated insulator continuously transitions into an electron correlated insulator at charge filling ν<sub>e</sub> = 1, suggesting a mixed correlated insulating state between the two limits. Our studies establish semiconducting moiré superlattices as an intriguing platform for engineering bosonic phases.