Correlated insulator of excitons in WSe2/WS2 moire superlattices

A panoply of unconventional electronic states has been observed in moire superlattices. Engineering similar bosonic phases remains, however, largely unexplored. We report the observation of a bosonic correlated insulator in tungsten diselenide/tungs ten disulfide (WSe2/WS2) moire 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 nex = 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 ne = 1, suggesting a mixed correlated insulating state between the two limits. Our studies establish semiconducting moire superlattices as an intriguing platform for engineering bosonic phases.

Automated summary

We observe a bosonic correlated insulator composed of excitons in tungsten diselenide/tungsten disulfide (WSe2/WS2) moire superlattices. The insulator transitions continuously into an electron correlated insulator with varying charge density, suggesting a mixed correlated insulating state between the two limits.