Electrical generation of equilibrium exciton fluid in semiconductor atomic double layers*

Bose-Einstein condensation of spatially indirect excitons is a fascinating macroscopic quantum phenomenon. Atomic double layers of transition metal dichalcogenide (TMD) semiconductor, which support large interlayer exciton binding energy, is an attractive platform to explore exciton condensation at high-temperatures and provides a route to realize high-temperature superconductivity. Although evidence of non-equilibrium exciton condensation has been observed in TMD double layers, the realization of an equilibrium exciton fluid, which is important for the realization of exciton superfluidity, remains elusive. Here we report the electrical generation of an equilibrium interlayer exciton fluid in WSe₂-hBN-MoSe₂ double layers. This is enabled by an improved dual-gate device design, in which excitons can be injected into the double layer system while interlayer tunneling is suppressed. Capacitance measurements further allow the quantification of the band alignment and exciton binding energy.