Phase Diagram of High-Temperature Electron-Hole Quantum Droplet in Two-Dimensional Semiconductors

Quantumliquids, systems exhibiting effects of quantum mechanicsand quantum statistics at macroscopic levels, represent one of themost exciting research frontiers of modern physical science and engineering.Notable examples include Bose-Einstein condensation (BEC),superconductivity, quantum entanglement, and a quantum liquid. However,quantum liquids are usually only stable at cryogenic temperatures,significantly limiting fundamental studies and device development.Here we demonstrate the formation of stable electron-hole liquid(EHL) with the quantum statistic nature at temperatures as high as700 K in monolayer MoS2 and elucidate that the high-temperatureEHL exists as droplets in sizes of around 100-160 nm. We alsodevelop a thermodynamic model of high-temperature EHL and, based onthe model, compile an exciton phase diagram, revealing that the ionizedphotocarrier drives the gas-liquid transition, which is subsequentlyvalidated with experimental results. The high-temperature EHL providesa model system to enable opportunities for studies in the pursuitof other high-temperature quantum liquids. The results can also allowfor the development of quantum liquid devices with practical applicationsin quantum information processing, optoelectronics, and optical interconnections.

Automated summary

Quantum liquids, such as Bose-Einstein condensates and superconductors, have been a vibrant area of research in modern physics and engineering. However, these quantum liquids are typically only stable at very low temperatures, which limits their practical applications. In this study, we demonstrate the existence of a stable electron-hole liquid at temperatures as high as 700 K in monolayer MoS2. We also develop a thermodynamic model and an exciton phase diagram to understand the gas-liquid transition in this high-temperature electron-hole liquid.