The ability to probe and control light-matter interaction at the nanometer scale not only advances frontiers of fundamental science, but also is a critical prerequisite to device applications in electronics, sensing, catalysis, energy harvesting, and more. Exploiting and enhancing the originally weak light-matter interactions via nanofabricated photonic structures; we will be able to sense chemical species at single molecule levels, to devise better imaging and manufacturing tools, to transfer data more efficiently at higher speed. In this invited talk, I will present recent progress in Prof. Xiang Zhang's group on the subject of light-matter interaction in perovskites.
The formation of half-light half-matter quasiparticle exciton polariton and its condensation in semiconductor microcavities are striking phenomena for the macroscopically quantum coherence at elevated temperature. The matter constituent of exciton polariton dictates the interacting behaviors of these bosonic particles primarily via exciton-exciton interactions. However, these interactions are all limited to the ground state exciton, although they are expected to be much stronger at Rydberg states with higher principal numbers. Here, for the first time, we observe the spontaneous formed Rydberg exciton polaritons (REPs) in a high quality Fabry-Perot cavity embedded with single crystal inorganic perovskite. Such REPs exhibit strong nonlinear behavior and anisotropic, enabling an anomalous dynamic process that leads to a coherent polariton condensate with prominent blue shift. This discovery presents a unique platform to study quantum coherent many-body physics, and enables unprecedented manipulation of these Rydberg states by new means such as chemical composition engineering, structural phase control, and external gauge fields. The solid state REP and its condensates also hold great potential for important applications, such as sensing, communication, and quantum computing.
Monolayer transition metal dichalcogenides (TMD) with confined 2D Wannier-Mott excitons are intriguing for the fundamental study of strong light-matter interactions and the applications of exciton-polaritons based devices at high temperatures. However, the research of 2D exciton-polaritons has been hindered, because the polaritons in these atomically thin semiconductors discovered so far can hardly support strong nonlinear interactions and quantum coherence due to uncontrollable polariton dynamics and weakened coherent coupling. In this work, we demonstrate, for the first time, precisely controlled hybrid composition with angular dependence and dispersion-correlated polariton emission by tuning the polariton dispersion in TMD over a broad temperature range of 110-230 K in a single cavity. This tamed polariton emission is achieved by the realization of robust coherent exciton-photon coupling in a monolayer tungsten disulphide (WS2) with large splitting-to-linewidth ratios (SLR, >3.3). The unprecedented ability to manipulate the dispersion and correlated properties of TMD exciton-polariton at will offers new possibilities to explore important quantum phenomena such as Bose–Einstein condensation (BEC) and superfluidity, but also holds great promise to applications for the inversionless lasers and valleytronic devices.