Inter-layer moiré biexciton and its stabilization

In twisted hetero-bilayers, a unique class of excitons—inter-layer excitons—arises when electrons and holes reside in separate layers due to a type-II heterojunction. These excitons possess a strong out of plane permanent dipole moment. This allows the excitons to be widely tuneable by various external stimuli. More complex behaviours emerge when these are placed in a periodic potential landscape emerging from a moiré superlattice.

In this work, we report on the interactions among these moiré excitons. Our findings show an attractive interaction between the excitons, contrary to the current consensus. Our technique of funnelling these interlayer excitons to a specific location achieves a high exciton density even at lower excitation powers. This combined with the attractive interaction, allows us to probe stable biexciton and higher order interlayer moiré excitons.