arXiv subjects

Boris Louis

Publications and source records attributed to Boris Louis.

4 recordsLinked to original sources

arXiv2026

Room Temperature Collective Blinking and Photon Bunching from CsPbBr3 Quantum Dot Superlattice

Development of quantum light sources and search for quantum systems capable of supporting collective many-body states are crucial for further progress of modern quantum technologies. Metal halide perovskite quantum dots (QDs) have emerged as a promising candidate for quantum light sources, as individual QDs are reliable single photon emitters even at room temperature. However, photon bunching, a key signature of collective many-body states, has been so far largely observed at cryogenic temperatures in perovskite materials, limiting their applications under ambient conditions. Here, we report the observation of collective blinking and photon bunching in perovskite QD superlattices at room temperature. Sub-wavelength-sized (100 - 500 nm) CsPbBr3 QD superlattices, fabricated via a self-assembly process, exhibit an unusual two-level blinking behavior similar to that of single QDs, and demonstrate photon bunching with a degree of up to 2.75. Time-resolved photoluminescence (PL) measurements and super-resolution imaging reveal that the superlattices have a significantly longer PL lifetime than individual QDs and that their emission is spatially confined to regions tens of nanometers in size. These observations suggest long-range exciton migration to a localized energy trap within the superlattice. Excitation power dependent degree of bunching and analysis of the bunching dynamics indicate that the photon bunching originates from exciton-biexciton cascade emission, a key mechanism for generating entangled photons. These findings establish perovskite QD superlattices as a promising platform for room-temperature collective optical phenomena and quantum light generation, advancing scalable quantum photonic technologies.

physics.optics↗

arXiv2025

M3Scope a 3D multimode multiplane microscope for imaging nanoscale dynamics in soft matter

Fast, volumetric imaging that integrates multiple imaging modalities is essential for probing dynamic, heterogeneous soft and biological matter. Here, we present the M3Scope, a simple yet versatile multiplane microscope that extends widefield detection with a modular multimode cube to enable dual color fluorescence, polarization-resolved, and correlative brightfield fluorescence imaging while (i) preserving simultaneous 3D acquisition at high frame rates (100 fps) and (ii) requiring minimal realignment. We demonstrate its potential by investigating polymer dynamics across multiple spatial and temporal scales. In an acrylamide type polymerizing network, dual color tracking of 100 nm and 300 nm fluorescent probes revealed size dependent viscosities diverging from 15 mPa.s to 40 mPa.s after gelation. Polarization resolved rotational tracking of gold bipyramids yielded viscosities within 10 percent of theoretical values in 80 to 95 percent glycerol and remained accurate in the high-viscosity regime (bigger than 400 mPa.s) where translational motion is undetectable. Fluorescence brightfield imaging correlated structural changes during poly(isopropyl acrylamide) (pNIPAM) phase separation as well as variations in tracer diffusivity, linking morphology and dynamics in 3D. Taken together, these results show that the M3Scope delivers high speed volumetric imaging with flexible modality switching, providing a powerful platform for studying dynamic, heterogeneous systems across disciplines, from polymer physics to cell mechanobiology.

physics.optics↗

arXiv2025

Microscopic Intricacies of Self-Healing in Halide Perovskite-Charge Transport Layer Heterostructures

The stability and performance of halide perovskite photovoltaic devices are critically limited by progressive defect generation and associated local non-radiative losses during operation. Self-healing of defects provides a promising pathway to prolong device functionality, yet the underlying microscopic mechanisms remain poorly understood, particularly the role of interfacial chemistry on trap dynamics and healing kinetics. Here, we elucidate self-healing and defect evolution in triple-cation mixed halide (TCMH) perovskite films and their device-relevant charge transport layer heterostructures subjected to photo-induced damage. Using correlation clustering imaging (CLIM), our recently developed local functional imaging tool, we map spatiotemporal photoluminescence heterogeneity to track defect dynamics in pristine and heterostructure films. The defect healing follows bi-phasic kinetics, with an initial electronic relaxation (tens of minutes) and a subsequent slower phase (~ hours) associated to ionic and lattice rearrangement. Most importantly, our results demonstrate that the chemical nature of charge-transport layers modulates trap activity, healing kinetics, and halide redistribution, with heterostructures exhibiting faster recovery than pristine films, a boon for device resilience. These findings provide new insights into the dynamic interaction between defects, interfaces, and ion migration, and establish a framework for rational design of durable, next-generation perovskite optoelectronic devices.

cond-mat.mtrl-sci↗

arXiv2025

Three-dimensional Optical Reconstruction of colloidal electrokinetics via multiplane imaging

Sorting, filtering, moving and controlling colloidal particles is crucial in many fields, ranging from chemistry to biology and physics. Dielectrophoresis is an outstanding tool for the manipulation of small particles by AC electric fields, due to its high selectivity and the absence of the need for labels. We use a new theoretical-experimental approach to study the dynamics of fluorescently labeled polystyrene nanoparticles of 200 nm under positive and negative dielectrophoresis conditions. Our multiplane widefield microscopy technique combined with single particle tracking offers real-time ($>$ 100 fps) superresolved visualization of colloidal dynamics in three spatial dimensions. This real-time 3D imaging technique allows the reconstruction of superresolved trajectories, enabling the visualisation of local forces with unprecedented detail. To interpret this data, a dedicated multiscale modeling approach was developed, targeting a direct comparison between theory and experiment. In the current model DEP and electro-osmotic forces were considered. Under positive DEP conditions, this resulted in a very good agreement with experiment. Under negative DEP conditions, the agreement is less clear, indicating the importance of other effects. This illustrates the potential of this combined 3D imaging and modeling approach to validate and refine our theoretical understanding of AC field induced colloidal dynamics. This framework is broadly applicable to other complex fluid or microfluidic motion.

cond-mat.soft↗