Abstract:

Colloidal quantum dots (CQDs) offer a tunable and technology-compatible platform for quantum light-matter interactions and the inspiring technology that comes along with it. However, understanding the dynamics of electronic excitation is tremendously challenging. In large part, this is because it warrants access to multiple time scales, from picoseconds to minutes. In this talk, I will present some of the recent progress we and others are making to accomplish this goal.

Starting from the slower part of the time-scale range, fluctuations in the energy of the photons emitted by a single CQDs pose a significant hurdle towards their application as source of quantum light. Recently, we have pinpointed the Stark effect as the sole mechanism responsible for such fluctuations in II-VI semiconductor colloidal quantum dots [1]. On the other hand, preliminary experiments suggest that this is not the case in the promising new member of the quantum-emitter family, halide-perovskite nanocrystals (HPNCs). In search for alternative explanations, we have implemented heralded spectroscopy [2], a new spectroscopic technique enabling us to measure spectral fluctuations down to the nanosecond time scale. Our observations suggest that spectral noise in HPNCs occurs due fluctuations in the crystal structure. Surprisingly, we observe a laser-power-dependent switch of the crystal structure to a high-symmetry state, suggesting the formation of transient dynamical ordering.

[1]          F. Conradt et al., Nano Lett. 23, 9753 (2023).

[2]          G. Lubin et al., Nano Letters 21, 6756 (2021).

Figure 1: Heralded spectroscopy to follow fast electronic fluctuation in a single QD