Abstract
Colloidal semiconductor quantum dots (QDs) are attractive materials that provide unique photophysics of multiple electron-hole pairs (multiexcitons) in strongly quantum confined systems. Multiexciton phenomena such as efficient Auger recombination have been intensively investigated with respect to individual QDs. However, the cooperative nature of QDs, especially in terms of multiexciton coherence, has not been elucidated thus far. Here, we report the observation of the collective enhancement of quantum coherence in coupled QD films. Using a photocurrent quantum interference technique, we find that the multiexciton quantum coherence in coupled QDs is significantly increased compared to the case of isolated QDs. This cooperative effect is induced by the coherent electronic coupling between QDs. Our results clarify the enhancement mechanism in coupled quantum systems and open the door to advanced optoelectronic applications such as coherent amplifiers and frequency upconverters.
Highlights
Colloidal semiconductor quantum dots (QDs) are attractive materials that provide unique photophysics of multiple electron-hole pairs in strongly quantum confined systems
We report the observation of the collective enhancement of quantum coherence in coupled QD films
Using a photocurrent quantum interference technique, we find that the multiexciton quantum coherence in coupled QDs is significantly increased compared to the case of isolated QDs
Summary
Colloidal semiconductor quantum dots (QDs) are attractive materials that provide unique photophysics of multiple electron-hole pairs (multiexcitons) in strongly quantum confined systems. The overlap of electronic wave functions is expected to increase the interdot tunneling rate for the photocurrent measurement, and affect cooperative amplification through the quantum coherence shared by the coupled QDs. Here, we demonstrate the collective enhancement of quantum coherence in coupled QD films. In order to determine coherent processes from photocurrent signals, we perform photocurrent quantum interference measurements by using a phase stabilization technique of excitation pulses.
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