Direct observation of metastable hot trions in an individual quantum dot

Magnetophotoluminescence and excitation spectroscopy are used to probe the excited-state spectrum of negatively charged trions in an InGaAs quantum dot. A single dot optical charging device allows us to selectively prepare a specific few (1e, 2e) electron states and stabilize hot trions against decay via electron tunneling from excited orbital states. The spin structure of the excited state results in the formation of metastable trions with strong optical activity that are directly observed in luminescence. Excitation spectroscopy is employed to map the excited singlet and triplet states of the two-electron wave function, and fine-structure splittings are measured for the lowest-lying and excited orbital states. Magneto-optical measurements allow us to compare the g factors and diamagnetic response of different trion states.