Stark Spectroscopy and Radiative Lifetimes in Single Self-Assembled CdTe Quantum Dots

We present studies on Coulomb interactions in single self-assembled CdTe quantum dots. We use a field effect structure to tune the charge state of the dot and investigate the impact of the charge state on carrier wave functions. The analysis of the quantum confined Stark shifts of four excitonic complexes allows us to conclude that the hole wave function is softer than electron wave function, i. e. it is subject to stronger modifications upon changing of the dot charge state. These conclusions are corroborated by time-resolved photoluminescence studies of recombination lifetimes of different excitonic complexes. We find that the lifetimes are notably shorter than expected for strong confinement and result from a relatively shallow potential in the valence band. This weak confinement facilitates strong hole wave function redistributions. We analyze spectroscopic shifts of the observed excitonic complexes and find the same sequence of transitions for all studied dots. We conclude that the universality of spectroscopic shifts is due to the role of Coulomb correlations stemming from strong configuration mixing in the valence band.Comment: sent to Physical Review

Macroscopic coherence of a single exciton state in a polydiacetylene organic quantum wire

We show that a single exciton state in an individual ordered conjugated polymer chain exhibits macroscopic quantum spatial coherence reaching tens of microns, limited by the chain length. The spatial coherence of the k=0 exciton state is demonstrated by selecting two spatially separated emitting regions of the chain and observing their interference.Comment: 12 pages with 2 figure

Exciton dans un fil quantique organique

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Nature du désordre et propriétés optiques des excitons dans les fils quantiques semi-conducteurs (de la boîte au fil)

LIMOGES-ENSCI (870852305) / SudocPARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Non-linear optics on an exciton state in a single quantum dot

International audienceWe report on non-linear effects on the exciton ground state in a single quantum dot, driven by a strong resonant optical field. The resonant excitation is achieved by embedding the quantum dots in a waveguiding structure. Thus, the light-matter coupling is enhanced, allowing the observation of Rabi oscillations up to three periods. With increasing pulse area, a decrease of the exciton lifetime is observed leading to a very rapid damping of the oscillations amplitude. Resonant coherent control experiments show that the coherence time of the ground exciton state in a single quantum dot is fast, of the order of a few tens of picoseconds