Electron-hole Liquid in Direct Bandgap Semiconductor at Room Temperature

The condensation of charge carriers in semiconductors known as electron-hole liquid (EHL) represents a macroscopic quantum state of matter, where a bunch of correlated particles form the tiny droplets that behave as a collective state of a single entity. Due to primary obstacles of excess thermal energy, short carrier lifetime, and low binding energy, EHL is realized only under extreme conditions, like cryogenic temperature and in materials having multivalley indirect band-structure, restricting their potential applications. Here we present our results of the first observation of EHL in the direct bandgap metal halide perovskite nanocrystals at ambient temperature. In our measurements the polarization resolved transient absorption technique employed to investigate the EHL state, where the opposite circularly polarized light pulses reveal the ground state of EHL below the exciton and biexciton states. Further EHL’s condensation and evaporation processes are monitored by excited state absorption of the droplets. By theoretical calculation critical temperature of 386 K and critical density of 8×10¹⁸ cm^-3 is estimated. Our study will pave the way for the development of quantum phenomena-based technologies and provide a new platform to understand the many-body correlated effect of quantum materials.