AP Seminar - Manipulating Quantum Fluids of Light at Room Temperature

Semiconductor materials have a wide range of elemental excitations or quasi-particles derived from the band structures and electron-phonon-photon couplings, which profoundly impact the transport properties and optical responses. When a semiconductor is embedded into a microcavity, the exciton and microcavity photons form a new quantum superposition between exciton and photon, called microcavity exciton polariton. This “part-light part-matter” bosonic particles exhibit extremely small effective mass and strong nonlinear interactions, underpinning the fascinating macroscopic quantum state of nonequilibrium Bose-Einstein condensation (BEC). This macroscopic quantum phenomenon are coined as quantum fluids of light. BEC were previously observed in cold atom system in ~ hundreds of nano-Kelvin, recent progress in a wide range of semiconductor gain materials made it possible to realize polariton BEC at elevated temperatures even at room temperature. In this talk, we will first focus on the realization of room-temperature polariton BEC and lasing in halide perovskite semiconductor and two-dimensional semiconductor microcavities, the typical spectroscopic signatures such as threshold, statistics of particle occupation and temporal-spatial coherence. Then we will discuss how artificial potential landscape can be harnessed to control the condensate towards new functionalities, e.g., topologically protected edge and corner states. Finally, we will present how the nonlinear interactions can be characterized and utilized for ultrafast optical switching, advocating the strong promise of exciton polariton towards future quantum simulator and integrated optoelectronics.