Phonon-Mediated Relaxation from Including Non-adiabatic Couplings of Time-domain DFT in Kadanoff-Baym-Keldysh Technique
Hadassah Griffin

Ph.D. Candidate,
Physics, NDSU

Monday, December 2, 3:00-4:00pm, South Engineering 208

Refreshments at 2:30, South Engineering 208 (online visit)

Abstract:

Applications of heterostructured nanomaterials, such as Janus semiconductor nanocrystals (NCs), require a quantitative understanding of their photoexcited properties. Here, we study photoexcited state time evolution of a Si QD, a reference PbSe NC, and several 1.9 nm Janus NCs made of Cd, Pb, and Se by employing the Boltzmann transport equation (BE), which allows for competition between different relaxation channels such as phonon-mediated carrier thermalization, exciton transfer, and exciton multiplication and recombination. BE collision integrals are computed using finite-temperature many-body perturbation theory (sometimes called Kadanoff-Baym-Keldysh (KBK) technique) based on density functional theory (DFT) simulations. Exciton effects are included by solving the Bethe-Salpeter equation, with additional simplifying approximations, and incorporating exciton energies and states into the collision integrals. Phonon-mediated relaxation is included by utilizing on-the-fly nonadiabatic coupling data from DFT-based finite-temperature molecular dynamics simulations in the KBK technique. Rates calculated from the collision integrals can be used to calculate internal quantum efficiency (the number of excitons generated from a single absorbed energetic photon).

Author bio:

Hadassah Griffin is a PhD student at the North Dakota State University Department of Physics. Her research advisor is Dr. Andrei Kryjevski. She started her B. S. Physics degree at Brigham Young University in Provo and completed it at Brigham Young University---Idaho in 2021. She obtained her M.S. in Physics from North Dakota State University in May 2024.

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