Room-Temperature Electron-Hole Liquid in Monolayer MoS₂

Excitons in semiconductors are usually noninteracting and behave like an ideal gas, but may condense to a strongly correlated liquid-like state, i.e., electron-hole liquid (EHL), at high density and appropriate temperature. An EHL is a macroscopic quantum state with exotic properties and represents the ultimate attainable charge excitation density in steady states. It bears great promise for a variety of fields such as ultra-high-power photonics and quantum science and technology. However, the condensation of gas-like excitons to an EHL has often been restricted to cryogenic temperatures, which significantly limits the prospect of EHLs for use in practical applications. Herein we demonstrate the formation of an EHL at room temperature in monolayer MoS₂ by taking advantage of the monolayer's extraordinarily strong exciton binding energy. This work demonstrates the potential for the liquid-like state of charge excitations to be a useful platform for the studies of macroscopic quantum phenomena and the development of optoelectronic devices.