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Exciton-driven change of phonon modes causes strong temperature dependent bandgap shift in nanoclusters

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Title
Exciton-driven change of phonon modes causes strong temperature dependent bandgap shift in nanoclusters
Author(s)
Muckel, F; Lorenz, S; Jiwoong Yang; Nugraha, TA; Scalise, E; Taeghwan Hyeon; Wippermann, S; Bacher, G
Subject
QUANTUM DOTS, ; ENERGY-GAP, ; CDSE, ; LUMINESCENCE, ; SURFACE, ; SI, ; NANOPARTICLES, ; TRANSITION, ; PEROVSKITE
Publication Date
2020-12
Journal
NATURE COMMUNICATIONS, v.11, no.1, pp.4127
Publisher
NATURE PUBLISHING GROUP
Abstract
© The Author(s) 2020. The fundamental bandgap E-g of a semiconductor-often determined by means of optical spectroscopy-represents its characteristic fingerprint and changes distinctively with temperature. Here, we demonstrate that in magic sized II-VI clusters containing only 26 atoms, a pronounced weakening of the bonds occurs upon optical excitation, which results in a strong exciton-driven shift of the phonon spectrum. As a consequence, a drastic increase of dE(g)/dT (up to a factor of 2) with respect to bulk material or nanocrystals of typical size is found. We are able to describe our experimental data with excellent quantitative agreement from first principles deriving the bandgap shift with temperature as the vibrational entropy contribution to the free energy difference between the ground and optically excited states. Our work demonstrates how in small nanoparticles, photons as the probe medium affect the bandgap-a fundamental semiconductor property. The bandgap of nanostructures usually follows the bulk value upon temperature change. Here, the authors find that in small nanocrystals a weakening of the bonds due to optical excitation causes a pronounced phonon shift, leading to a drastic enhancement of the bandgap's temperature dependence
URI
https://pr.ibs.re.kr/handle/8788114/7528
DOI
10.1038/s41467-020-17563-0
ISSN
2041-1723
Appears in Collections:
Center for Nanoparticle Research(나노입자 연구단) > 1. Journal Papers (저널논문)
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