Lattice distortion inducing exciton splitting and coherent quantum beating in CsPbI3 perovskite quantum dots
Abstract
Anisotropic exchange splitting in semiconductor quantum dots results in bright-exciton fine-structure splitting important for quantum information processing. Direct measurement of fine-structure splitting usually requires single/few quantum dots at liquid-helium temperature because of its sensitivity to quantum dot size and shape, whereas measuring and controlling fine-structure splitting at an ensemble level seem to be impossible unless all the dots are made to be nearly identical. Here we report strong bright-exciton fine-structure splitting up to 1.6 meV in solution-processed CsPbI3 perovskite quantum dots, manifested as quantum beats in ensemble-level transient absorption at liquid-nitrogen to room temperature. The splitting is robust to quantum dot size and shape heterogeneity, and increases with decreasing temperature, pointing towards a mechanism associated with orthorhombic distortion of the perovskite lattice. Effective-mass-approximation calculations reveal an intrinsic `fine-structure gap' that agrees well with the observed fine-structure splitting. This gap stems from an avoided crossing of bright excitons confined in orthorhombically distorted quantum dots that are bounded by the pseudocubic {100} family of planes.
- Publication:
-
Nature Materials
- Pub Date:
- November 2022
- DOI:
- 10.1038/s41563-022-01349-4
- arXiv:
- arXiv:2206.13716
- Bibcode:
- 2022NatMa..21.1282H
- Keywords:
-
- Condensed Matter - Mesoscale and Nanoscale Physics
- E-Print:
- doi:10.1038/s41563-022-01349-4