Biplab K. Patra | Searcharxiv

arXiv2021

Intermittency of CsPbBr$_3$ perovskite quantum dots analyzed by an unbiased statistical analysis

We analyze intermittency in intensity and fluorescence lifetime of CsPbBr$_3$ perovskite quantum dots by applying unbiased Bayesian inference analysis methods. We apply changepoint analysis (CPA) and a Bayesian state clustering algorithm to determine the timing of switching events and the number of states between which switching occurs in a statistically unbiased manner, which we have benchmarked particularly to apply to highly multistate emitters. We conclude that perovskite quantum dots display a plethora of gray states in which brightness broadly speaking correlates inversely with decay rate, confirming the multiple recombination centers model. We leverage the CPA partitioning analysis to examine aging and memory effects. We find that dots tend to return to the bright state before jumping to a dim state, and that when choosing a dim state they tend to explore the entire set of states available.

cond-mat.mes-hall↗

arXiv2021

Fano lineshapes and Rabi splittings: Can they be artificially generated or obscured by the numerical aperture?

Fano resonances and Rabi splittings are routinely reported in the scientific literature. Asymmetric resonance lineshapes are usually associated with Fano resonances, and two split peaks in the spectrum are often attributed to a Rabi splitting. True Fano resonances and Rabi splittings are unequivocal signatures of coherent coupling between subsystems. However, can the same spectral lineshapes characterizing Fano resonances and Rabi splittings arise from a purely incoherent sum of intensities? Here we answer this question through experiments with a tunable Fabry-Pérot cavity containing a CsPbBr\textsubscript{3} perovskite crystal. By measuring the transmission and photoluminescence of this system using microscope objectives with different numerical aperture ($NA$), we find that even a modest $NA=0.4$ can artificially generate Fano resonances and Rabi splittings. We furthermore show that this modest $NA$ can obscure the anti-crossing of a bona fide strongly coupled light-matter system. Through transfer matrix calculations we confirm that these spectral artefacts are due to the incoherent sum of transmitted intensities at different angles captured by the $NA$. Our results are relevant to the wide nanophotonics community, characterizing dispersive optical systems with high numerical aperture microscope objectives. We conclude with general guidelines to avoid pitfalls in the characterization of such optical systems.

physics.optics↗