Atomistically resolved hot exciton relaxation dynamics in CdSe quantum dots: Experiment and theory

Journal Article · Sun Sep 14 00:00:00 EDT 2025 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/5.0272621· OSTI ID:2998202

Ghosh, Arnab; Peng, Kaiyue; Brosseau, Patrick J; Rabani, Eran; Kambhampati, Patanjali

Semiconductor quantum dots (QDs) are well known to give rise to a quantum confined structure of excitons. Because of this quantum confinement, new physics of hot exciton relaxation dynamics arises. Decades of work using transient absorption (TA) spectroscopy have yielded initial simple observations, such as estimates of the cooling rate from single pump photon energy experiments. More detailed TA experiments employed variable pump photon energies to measure excitonic state-resolved transition rates. These TA measurements, usually the simplest form, have been employed to characterize QDs and their relaxation dynamics to this day. Yet, these TA measurements are fundamentally lacking in their ability to measure energy-resolved hot exciton cooling, which requires observation of the full cooling history through the real excitonic manifold. Here, we employ coherent multi-dimensional spectroscopy (CMDS) to perform an atomistically directed study of hot exciton cooling in CdSe QDs, revealing energy resolved relaxation dynamics. CMDS experiments are compared with simulations and prior TA measurements and simpler theories. Our findings reveal a hot exciton relaxation dynamics landscape. This relaxation dynamics landscape is a linear or sub-linear function of excess energy for different structures of QDs, with a strong size dependence. Our model simulations parameterized by the empirical pseudopotential model reproduces the experimental functional form and the dependence upon QD diameter and shell.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: US Department of Energy; USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2998202
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 163
• Country of Publication: United States
• Language: English

Related Subjects

Atomistic simulations
Chemical dynamics
Excitation energies
Excitons
Optical parametric amplifiers
Phonons
Quantum confinement
Quantum dots
Quantum mechanical principles
Transient-absorption spectroscopy