Neck Barrier Tailors Photon Bunching Characteristics in Single Quantum Dot Dimer Molecules

Somnath Koley^a, Jiabin Cui^a, Yossef. E. Panfil^a, Uri Banin^a

^aThe Institute of Chemistry and Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem, Israel

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)

#NANOQ22. Colloidal Semiconductor nanocrystals for Quantum Technologies

Online, Spain, 2022 March 7th - 11th

Organizers: Francesco Di Stasio, Iwan Moreels and Riccardo Sapienza

Contributed talk, Somnath Koley, presentation 221
DOI: https://doi.org/10.29363/nanoge.nsm.2022.221
Publication date: 7th February 2022

Colloidal Quantum Dot (CQD) Molecules represents a new class of artificial molecules where the electron wavefunction in two neighboring CQD artificial atoms hybridizes within the connected nanocrystals. Like naturally occurring molecules, the electronic coupling strength is expected to manifest widely varied properties in CQD molecules, altering not only single-particle characteristics but also complex many-body interactions in CQDs. Herein, we discuss in detail the signatures of single CQD molecules at different coupling strengths, as reflected on their emitted photon statistics at room temperature. The neck diameter in CdSe/CdS core/shell CQD homodimer molecules allowed to tune the hybridization of the electron wavefunction at a fixed center-to-center distance. At small neck diameter, the electronic between two CQDs are weak, which increases progressively with neck filling. We show that the photophysical properties of CQD molecules at weak coupling regime are governed by strong localization of electron wavefunction at individual CQD atoms, whereas in the strong coupling regime, due to facile delocalization the CQD molecules resemble the properties of single artificial atoms. A radiative multi-exciton configuration is preferred in the photo-excited weakly coupled molecules mostly governed by dipole-interactions, leading to strong photon bunching. In the strong coupling regime, electron tunneling activates a unique Auger process leading to single-photon emission via dissociation of biexciton, from a system consisting of two CQDs. This study validates the analogy of CQD molecules with the bonding nature of naturally occurring molecules that exhibit distinct ionic and covalent types of bonding in different coupling regimes, manifesting different properties. A detailed spectroscopic signatures following the time-tagged-time-resolved data will be discussed. The demonstration of multitude opto-electronic configuration tuning the extent of hybridization brands the CQD molecules as novel building blocks for many applications such as in low-threshold lasing and single-photon emitter in quantum applications.

References:

[1] Cui, J.; Panfil, Y.E.; Koley, S.; Shamalia, D.; Waiskopf, N.; Remennik, S.; Popov, I.; Oded, M.; Banin, U. Colloidal Quantum Dot Molecules Manifesting Quantum Coupling at Room Temperature. Nature Commun. 2019, 10, 1-10.

[2] Cui, J.; Koley, S; Panfil, Y. E.; Levi, A.; Ossia, Y.; Waiskopf, N.; Remennik, S.; Oded, M.; Banin, U. Neck Barrier Engineering in Quantum Dot Dimer Molecules via Intraparticle Ripening. J. Am. Chem. Soc. 2021, Article ASAP (DOI: 10.1021/jacs.1c08863).

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