||Harmonic Quantum Coherence of Multiple Excitons in PbS/CdS Core-Shell Nanocrystals
Tahara, Hirokazu ,
Sakamoto, Masanori ,
Teranishi, ToshiharuKanemitsu, Yoshihiko
2017-12-11 , American Physical Society (APS)
半導体ナノ粒子が光を電子へ変換する過程を解明 --高効率な太陽電池や光検出器への基礎メカニズム--. 京都大学プレスリリース. 2017-12-14.
The generation and recombination dynamics of multiple excitons in nanocrystals (NCs) have attracted much attention from the viewpoints of fundamental physics and device applications. However, the quantum coherence of multiple exciton states in NCs still remains unclear due to a lack of experimental support. Here, we report the first observation of harmonic dipole oscillations in PbS/CdS core-shell NCs using a phase-locked interference detection method for transient absorption. From the ultrafast coherent dynamics and excitation-photon-fluence dependence of the oscillations, we found that multiple excitons cause the harmonic dipole oscillations with ω, 2ω, and 3ω oscillations, even though the excitation pulse energy is set to the exciton resonance frequency, ω. This observation is closely related to the quantum coherence of multiple exciton states in NCs, providing important insights into multiple exciton generation mechanisms.