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

[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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