Bright-Exciton Fine-Structure Splittings in Single Perovskite Nanocrystals.

Here we show that, in single perovskite CsPbI_{3} nanocrystals synthesized from a colloidal approach, a bright-exciton fine-structure splitting as large as hundreds of μeV can be resolved with two orthogonally and linearly polarized photoluminescence peaks. This doublet could switch to a single peak when a single CsPbI_{3} nanocrystal is photocharged to eliminate the electron-hole exchange interaction. The above findings have prepared an efficient platform suitable for probing exciton and spin dynamics of semiconductor nanostructures at the visible-wavelength range, from which a variety of practical applications such as in entangled photon-pair source and quantum information processing can be envisioned.