[Crib-list] VIRTUAL Event... SPEAKER: Dipti Jasrasaria (UC, Berkeley/ CRIBB Seminar / 12:00 PM - 1:00 PM / Friday, June 3, 2022 (fwd)

[Shirley Entzminger]

    VIRTUAL Talk...

 	        COMPUTATIONAL RESEARCH in BOSTON and BEYOND SEMINAR
 				   (CRIBB)


   ZOOM meeting info...

 	https://mit.zoom.us/j/96155042770

 	Meeting ID: 961 5504 2770

====================================

DATE:	Friday, June 3, 2022

TIME:	12:00 PM - 1:00 PM


TITLE:	Interplay of Surface and Interior Modes in Exciton-Phonon
 	 Coupling at the Nanoscale


SPEAKER:   Dipti Jasrasaria  (UC, Berkeley)


ABSTRACT:

Quantum dots (QDs) are semiconducting nanocrystals that have been of much 
interest due to their highly tunable optoelectronic properties. These 
properties are greatly affected by coupling between excitons and phonons, or 
lattice vibrations, in these systems. Despite this, a microscopic picture of 
exciton-phonon coupling (EXPC) is still lacking, particularly regarding the 
magnitude and scaling with QD size, the dependence on phonon frequency, and the 
role of the QD surface. The computational complexity associated with accurately 
describing excitons and phonons has limited previous theoretical studies of 
EXPC to simplified models or very small QDs, which have limited transferability 
to experimental systems. Here, I will describe an atomistic approach for 
describing EXPC in QDs of experimentally relevant sizes. We validate our 
approach by calculating the reorganization energies, a measure of EXPC, for 
CdSe and CdSe-CdS core–shell QDs, finding good agreement with experimental 
measurements. We demonstrate that exciton formation distorts the QD lattice 
primarily along the coordinates of low-frequency acoustic modes. Modes at the 
NC surface play a significant role in smaller QDs while interior modes dominate 
for larger systems. This framework provides the foundation for ongoing work to 
compute phonon-mediated exciton dynamics in QDs.

=======================================

For information about the "Computational Research in Boston and Beyond Seminar"
(CRIBB), please visit:

 		https://math.mit.edu/sites/crib/


=================

Shirley A. Entzminger
Administrative Assistant II
Department of Mathematics
Massachusetts Institute of Technology
77 Massachusetts Avenue
Building 2, Room 350A
Cambridge, MA 02139
PHONE: 	(617) 253-4994
E-mail:	daisymae at math.mit.edu
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