Exciton lifetimes of CdTe nanocrystal quantum dots in high magnetic fields

We have measured the low-temperature (4.2 K) exciton lifetimes of zinc-blende CdTe nanocrystal quantum dots (NQDs), 2.6–3.8 nm in diameter, in magnetic fields up to 30 T. The exciton photoluminescence decay time decreases with both dot size and magnetic field. We explain the decrease in decay time in magnetic fields by the mixing of bright and dark exciton states due to a small shape asymmetry in the zinc-blende CdTe NQDs. We show that this behavior resembles that of wurtzite CdSe NQDs, and we demonstrate that an asymmetry of NQDs caused by either shape or crystal structure leads to similar exciton decay dynamics