Nonmonotonic size dependence of the dark/bright exciton splitting in GaAs nanocrystals

摘要: The dark/bright exciton splitting {Delta}{sub x} in semiconductor nanocrystals is usually caused by electron-hole exchange interactions. Since the wave-function overlap enhanced quantum confinement, it generally assumed that increases monotonically as quantum-dot size decreases. Using atomistic pseudopotential calculations, we show GaAs scales nonmonotonically with nanocrystal size. By analyzing wave functions terms of contributions from different k points bulk Brillouin zone, identify origin such nonmonotonic behavior a transition lowest conduction-band function {lambda} like to X radius decreases below 19{angstrom}. nonmonotonicity arises because long-range component interaction all but vanishes when electron becomes like. We also direct/indirect induced external pressure results sudden reduction x}.