期刊
NATURE COMMUNICATIONS
卷 11, 期 1, 页码 -出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41467-020-17563-0
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资金
- German Research Foundation DFG [Ba 1422/13-2]
- German Academic Exchange Service (DAAD)
- German Federal Ministry of Education and Research (BMBF)
- European Union (FP7-PEOPLE2013-COFUND) [605728]
- German Federal Ministry of Education and Research (BMBF) within the NanoMatFutur programme [13N12972]
- NERSC [35687]
- Research Center Program of the Institute for Basic Science (IBS) in Korea [IBS-R006-D1]
- DGIST Start-up Fund Program of the Ministry of Science, ICT and Future Planning [2019070014]
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.
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