arXiv subjects

Kaiyue Peng

Publications and source records attributed to Kaiyue Peng.

4 recordsLinked to original sources

arXiv2026

Selective Biexciton Generation Under Energy-Time Entangled Quantum Light in Quantum Dots

Energy-time entangled photons provide new opportunities for controlling multiphoton absorption beyond classical limits. Here, we investigate biexciton generation in nanocrystal quantum dots driven by energy-time-entangled quantum light generated via a spontaneous parametric down-conversion process. We show that quantum correlations can enhance biexciton production while suppressing excitonic populations. By employing a three-level model, we demonstrate that biexciton generation depends nontrivially on the photon arrival-time entanglement and the pump bandwidth. Consequently, we find that maximizing efficiency requires an optimally shaped entangled photon field rather than simply scaling parameters for a monotonic improvement. Extending to a realistic CdSe/CdS core-shell quantum dots containing many excitonic states coupled to the quantum field, we demonstrate that increasing the bi-photon arrival time entanglement (closer arrival time) enhances constructive pathway interference and expands accessible excitation channels while preserving a better energy conservation excitation than classical light when generating biexciton. Furthermore, tuning the time correlation properties enables selective excitation of closely spaced biexciton states. These results establish entangled quantum light as a powerful tool for selective excitation and control of nonlinear optical processes in quantum-confined systems.

physics.chem-ph↗

arXiv2026

Photoluminescence Line Shapes of Nanocrystals: Contributions from First- and Second-Order Vibronic Couplings

We present a microscopic, parameter-free approach for computing the photoluminescence spectra of a single semiconductor nanocrystal. The method derives exciton-phonon coupling directly from the semi-empirical pseudopotential framework and systematically incorporates both diagonal and off-diagonal interactions, expanded to second-order in the phonon modes. The dipole-dipole correlation function was calculated using a Dyson expansion within the Kubo-Toyozawa formalism, enabling a consistent description of the role of pure dephasing and population-transfer on the photoluminescence spectral features. Applied to CdSe/CdS core-shell nanocrystals, the approach quantitatively reproduces experimental photoluminescence spectra over a wide temperature range, revealing that quadratic phonon couplings account for nearly half of the homogeneous linewidth above 100-150 K, while off-diagonal couplings leading to exciton thermalization play only a minor role and only as T approaches 300K.

physics.chem-ph↗

arXiv2024

Polariton assisted incoherent to coherent excitation energy transfer between colloidal nanocrystal quantum dots

We explore the dynamics of energy transfer between two nanocrystal quantum dots placed within an optical microcavity. By adjusting the coupling strength between the cavity photon mode and the quantum dots, we have the capacity to fine-tune the effective coupling between the donor and acceptor. Introducing a nonadiabatic parameter, $γ$, governed by the coupling to the cavity mode, we demonstrate the system's capability to shift from the overdamped Forster regime ($γ\ll 1$) to an underdamped coherent regime ($γ\gg 1$). In the latter regime, characterized by swift energy transfer rates, the dynamics are influenced by decoherence times. To illustrate this, we study the exciton energy transfer dynamics between two closely positioned CdSe/CdS core/shell quantum dots with sizes and separations relevant to experimental conditions. Employing an atomistic approach, we calculate the excitonic level arrangement, exciton-phonon interactions, and transition dipole moments of the quantum dots within the microcavity. These parameters are then utilized to define a model Hamiltonian. Subsequently, we apply a generalized non-Markovian quantum Redfield equation to delineate the dynamics within the polaritonic framework.

cond-mat.mes-hall↗

arXiv2023

Polaritonic Bottleneck in Colloidal Quantum Dots

Controlling the relaxation dynamics of excitons is key to improving the efficiencies of semiconductor--based applications. Confined semiconductor nanocrystals (NCs) offer additional handles to control the properties of excitons, for example, by changing their size or shape, resulting in a mismatch between excitonic gaps and phonon frequencies. This has led to the hypothesis of a significant slowing--down of exciton relaxation in strongly confined NCs, but in practice due to increasing exciton--phonon coupling and rapid multiphonon relaxation channels, the exciton relaxation depends only weakly on the size or shape. Here, we focus on elucidating the nonradiative relaxation of excitons in NCs placed in an optical cavity. We find that multiphonon emission of carrier governs the decay resulting in a polariton--induced phonon bottleneck with relaxation timescales that are slower by orders of magnitude compared to the cavity--free case, while the photon fraction plays a secondary role.

cond-mat.mes-hall↗