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Physics of low-dimensional systems holds a lot of promise for technology. Among the various emerging materials, transition metal dichalcogenide materials are heralding a new era in optoelectronics and valleytronics owing to their unique properties. Photo-induced dynamics in these systems is mostly studied from the perspective of individual quasi-particles—excitons, bi-excitons, or, even, trions—their formation, evolution, and decay. The role of multi-body and exciton dynamics, the associated collective behavior, condensation, and inter-excitonic interactions remain intriguing and seek attention, especially in room-temperature scenarios that are relevant for device applications. This paper reports on novel findings on the formation and decay of an unexpected electron–hole quantum liquid phase at room-temperature on ultrafast timescales in multi-layer MoS2 nanoparticles, evidenced through femtosecond broadband transient absorption spectroscopy. The studies presented here reveal the complete dynamical picture: The authors employ a successful physical model using a set of coupled nonlinear rate equations governing the individual populations of these constituent phases to extract their contributions to bandgap renormalization. Beyond the observation of the electron–hole liquid-like state at room temperature, this work reveals the ultrafast dynamics of photo-excited low-dimensional systems arising out of collective many-particle behavior and correlations. The results of our numerical modeling and experiments on the formation and evolution of the excitonic condensates lead to the identification of this new paradigm, opening up ample scope for harnessing the electron–hole liquid at room temperature, in likely quantum devices.

The paper can be seen at
https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.202370056.