In quantum physics, Rydberg excitons with high principal value can exhibit strong dipole-dipole interactions. However, polaritons (quasiparticles) with an excitonic constituent in an excited state, known as Rydberg exciton polaritons (REPs) remain to be experimentally observed. In a recent study now published on the Proceedings of the National Academy of Sciences of the United States of America (PNAS). Wei Bao and an interdisciplinary research team in the departments of physics, electronics and the National Science Foundation (NSF) Nanoscale Science and Engineering Center in the U.S., observed the formation of REPs in a single crystal CsPbBr3 (cesium lead bromide) perovskite cavity; without any external fields. The researchers noted the polaritons to exhibit strong nonlinear behavior, which lead to a coherent polariton condensate with a prominent blue shift. The REPs in CsPbBr3 cavity were highly anisotropic (showing different properties in different directions) with a large extinction ratio due to the orthorhombic crystal structure of the perovskite.
Source:
https://phys.org/news/2019-09-rydberg-exciton-polaritons-condensate-perovskite.html