Atomistic tight-binding theory of excitonic splitting energies in CdX(X = Se, S and Te)/ZnS core/shell nanocrystals

作者：Sukkabot Worasak^*; Pinsook Udomsilp

来源：Superlattices and Microstructures, 2017, 101: 15-22.

DOI：10.1016/j.spmi.2016.11.015

• Tight-binding theory
• Excitonic splitting
• Electron-hole exchange interaction
• Core/shell nanocrystals

Using the atomistic tight-binding theory (TB) and a configuration interaction description (CI), we numerically compute the excitonic splitting of CdX(X = Se, S and Te)/ZnS core/ shell nanocrystals with the objective to explain how types of the core materials and growth shell thickness can provide the detailed manipulation of the dark-dark (DD), dark bright (DB) and bright-bright (BB) excitonic splitting, beneficial for the active application of quantum information. To analyze the splitting of the excitonic states, the optical band gaps, ground-state wave function overlaps and atomistic electron-hole interactions tend to be numerically demonstrated. Based on the atomistic computations, the single-particle and excitonic gaps are mainly reduced with the increasing ZnS shell thickness owing to the quantum confinement. In the range of the higher to lower energies, the order of the single particle gaps is CdSe/ZnS, CdS/ZnS and CdTe/ZnS core/shell nanocrystals, while one of the excitonic gaps is CdS/ZnS, CdSe/ZnS and CdTe/ZnS core/shell nanocrystals because of the atomistic electron-hole interaction. The strongest electron-hole interactions are mainly observed in CdSe/ZnS core/shell nanocrystals. In addition, the computational results underline that the energies of the dark-dark (DD), dark-bright (DB) and bright-bright (BB) excitonic splitting are generally reduced with the increasing ZnS growth shell thickness as described by the trend of the electron-hole exchange interaction. The high-to-low splitting of the excitonic states is demonstrated in CdSe/ZnS, CdTe/ZnS and CdS/ZnS core/shell nanocrystals because of the fashion in the electron-hole exchange interaction and overlaps of the electron-hole wave functions. As the resulting calculations, it is expected that CdS/ ZnS core/shell nanocrystals are the best candidates to be the source of entangled photons. Finally, the comprehensive information on the excitonic splitting can enable the use of suitable core/shell nanocrystals for the entangled photons in the application of quantum information.

• 出版日期2017-1