Multiexciton quantum interference in semiconductor nanocrystal quantum dots

Semiconductor nanocrystal quantum dots are one of the most suitable materials to examine strongly confined electron-hole pairs. It is desired to clarify their multiple carrier dynamics such as carrier multiplication and charged exciton properties. Here, we studied ultrafast multiexciton dynamics immediately after photoexcitation using quantum interference measurements [1]. The dipole oscillations containing single excitons, biexcitons, and triexcitons were observed by using the phase-locked interference detection method in transient absorption spectroscopy. We found that multiexcitons form harmonic quantum coherence, i.e., dipole oscillations with integer multiples of the exciton resonance frequency [2]. The coherent dynamics also play an important role in photogeneration processes of multiexcitons [3]. These results provide a deep understanding of multiexciton dynamics leading to advanced optoelectronic devices.

[1] H. Tahara and Y. Kanemitsu, Adv. Quantum Technol. (2019) in press.
[2] H. Tahara et al., Phys. Rev. Lett. 119, 247401 (2017).
[3] H. Tahara et al., Nat. Commun. 9, 3179 (2018).