arXiv subjects

Jehyeok Ryu

Publications and source records attributed to Jehyeok Ryu.

4 recordsLinked to original sources

arXiv2026

When blinking helps: enhanced single-photon purity in the off states of perovskite quantum dots

Photoluminescence blinking typically degrades the single-photon purity of quantum dot emission. Here, we show that individual CsPbBr$_3$ perovskite quantum dots (PQDs) can exhibit the opposite behavior: low-emitting off states are dimmer and shorter-lived, yet more strongly antibunched than high-intensity on states. Using time-correlated single-photon counting combined with state-resolved second-order correlation analysis, we identify a subset of PQDs in which the zero-delay second-order correlation, $g^{(2)}_0$, decreases upon switching from the on state to the off state, indicating improved single-photon purity. In the most pronounced case, $g^{(2)}_0$ decreases from 0.23 in the on state to 0.08 in the off state. We attribute this counterintuitive behavior to self-trapped-exciton-mediated suppression of the biexciton--exciton cascade, which suppresses multiphoton emission more effectively than single-exciton emission. These findings reveal an unconventional blinking regime in PQDs and show that blinking does not necessarily degrade single-photon purity.

cond-mat.mes-hall↗

arXiv2026

Size-dependent Dielectric Permittivity of Perovskite Nanocrystals

Perovskite nanocrystals (PNCs) are promising building blocks for quantum photonic devices. Optical properties of PNCs can be enhanced by integration with optical cavities or nanoantennas. Designing such structures requires accurate size dependent dielectric permittivity of PNCs. However, current reports provide primarily ensemble averaged values with limited access to the intrinsic response of individual PNCs. Here we suggest a methodology to reconstruct the size dependent complex dielectric permittivity of CsPbBr3 PNCs from the measured absorbance spectrum of colloidal solution. The permittivity of PNCs is modeled as a sum of Voigt profile oscillators, with the size dependent transition energies governed by the exciton effective mass. Using a transmission electron microscopy derived size distribution of the PNCs, the solution permittivity is obtained via Maxwell Garnett effective medium approximation. This permittivity is used in a transfer matrix method to simulate and fit the absorbance spectrum, from which the permittivity of PNCs is reconstructed. The extracted spectral linewidth from the imaginary part of the permittivity (78.4 meV) is consistent with single nanocrystal emission linewidths at room temperature. Finite element simulations show enhanced absorption cross section of a single PNC coupled to a nanoantenna, demonstrating applicability of the extracted permittivity. More generally, these findings provide a route to extract intrinsic permittivity of individual nanocrystals from absorbance measurements of their ensembles.

physics.optics↗

arXiv2025

Nickel Doping Unlocks Ambient-condition Photostability in Individual Cesium Lead Bromide Perovskite Quantum Dots

Developing efficient single-photon sources is fundamental to advancing photonic quantum technologies. In particular, achieving scalable, cost-effective, stable, high-rate, and high-purity single-photon emission at ambient conditions is paramount for free-space quantum communication. However, fulfilling all the requirements simultaneously under ambient conditions has remained a significant challenge. Here, the scalable, cost-effective ambient condition synthesis of nickel doped (Ni doped) CsPbBr3 perovskite quantum dots (NPQDs) is presented using a modified ligand-assisted reprecipitation (LARP) method. The resulting individual NPQDs demonstrate remarkable photostability, sustaining their performance for over 10 minutes under ambient conditions with environment humidity of ~55%, and exhibit exceptional single-photon purity (>99%) with a narrow emission linewidth (~70 meV). The remarkable photostability could be attributed to the spatial localization of exciton by Ni atoms on the surface of the nanocrystal, reducing its interaction with the environment. Our results demonstrated that NPQDs with outstanding combinations of quantum emitting properties can be both synthesized and operated at ambient conditions. These findings mark a significant step toward scalable, cost-effective quantum light sources for real-world applications, paving the way for robust quantum communication systems and devices.

cond-mat.mtrl-sci↗

arXiv2025

Perovskite Nanocrystals as Emerging Single-Photon Emitters: Progress, Challenges, and Opportunities

Metal-halide perovskite nanocrystals (PNCs) have emerged as leading candidates for next-generation quantum emitters, offering a unique combination of high photoluminescence quantum yield, tunable emission, short radiative lifetimes, and record-high single-photon purity under ambient conditions. These properties, together with low-cost and scalable solution-phase fabrication, position PNCs as attractive alternatives to traditional epitaxial and colloidal quantum dots. In this Review, we outline the physical parameters that define quantum emission in PNCs, compare their performance to other established and emerging quantum emitters, and assess the key figures of merit, including photostability, single-photon purity, and photon indistinguishability, required for practical quantum applications. We discuss underlying mechanisms affecting PNC emission behavior and highlight recent advances in improving their quantum emitting properties through synthetic and photonic engineering approaches. While challenges related to environmental stability and photon indistinguishability remain, emerging strategies, such as surface passivation, metal ion doping, and coupling with electromagnetic nano- and micro-cavities, are steadily closing the gap between PNCs and ideal quantum light sources.

physics.optics↗