Diffusivity Reveals Three Distinct Phases Of Interlayer Excitons In Mose2/Wse2 Heterobilayers

Charge separated interlayer excitons in transition metal dichalcogenide heterobilayers are being explored for moire exciton lattices and exciton condensates. The presence of permanent dipole moments and the poorly screened Coulomb interaction make many-body interactions particularly strong for interlayer excitons. Here we reveal two distinct phase transitions for interlayer excitons in the MoSe2/WSe2 heterobilayer using time and spatially resolved photoluminescence imaging: from trapped excitons in the moire potential to the modestly mobile exciton gas as exciton density increases to n(ex) similar to 10(11) cm(-2) and from the exciton gas to the highly mobile charge separated electron-hole plasma for n(ex) > 10(12) cm(-2). The latter is the Mott transition and is confirmed in photoconductivity measurements. These findings set fundamental limits for achieving quantum states of interlayer excitons.