Tuning moire excitons and correlated electronic states through layer degree of freedom

Moire coupling in transition metal dichalcogenides (TMDCs) superlattices introduces flat minibands that enable strong electronic correlation and fascinating correlated states, and it also modifies the strong Coulomb-interaction-driven excitons and gives rise to moire excitons. Here, we introduce the layer degree of freedom to the WSe2/WS2 moire superlattice by changing WSe2 from monolayer to bilayer and trilayer. We observe systematic changes of optical spectra of the moire excitons, which directly confirm the highly interfacial nature of moire coupling at the WSe2/WS2 interface. In addition, the energy resonances of moire excitons are strongly modified, with their separation significantly increased in multilayer WSe2/monolayer WS2 moire superlattice. The additional WSe2 layers also modulate the strong electronic correlation strength, evidenced by the reduced Mott transition temperature with added WSe2 layer(s). The layer dependence of both moire excitons and correlated electronic states can be well described by our theoretical model. Our study presents a new method to tune the strong electronic correlation and moire exciton bands in the TMDCs moire superlattices, ushering in an exciting platform to engineer quantum phenomena stemming from strong correlation and Coulomb interaction. Twisted heterostructures of transition metal dichalcogenides host the so-called moire excitons, or intralayer excitons modified by the moire potential. Here the authors show tunability of the moire excitons and the coexisting correlated electronic states in WSe2/WS2 superlattices with varying WSe2 layer thickness