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- Title
Exciton polarizability in semiconductor nanocrystals.
- Authors
Wang, Feng; Shan, Jie; Islam, Mohammad A.; Herman, Irving P.; Bonn, Mischa; Heinz, Tony F.
- Abstract
The response of charge to externally applied electric fields is an important basic property of any material system, as well as one critical for many applications. Here, we examine the behaviour and dynamics of charges fully confined on the nanometre length scale. This is accomplished using CdSe nanocrystals of controlled radius (1–2.5 nm) as prototype quantum systems. Individual electron–hole pairs are created at room temperature within these structures by photoexcitation and are probed by terahertz (THz) electromagnetic pulses. The electronic response is found to be instantaneous even for THz frequencies, in contrast to the behaviour reported in related measurements for larger nanocrystals and nanocrystal assemblies. The measured polarizability of an electron–hole pair (exciton) amounts to ∼104 Å3 and scales approximately as the fourth power of the nanocrystal radius. This size dependence and the instantaneous response reflect the presence of well-separated electronic energy levels induced in the system by strong quantum-confinement effects.
- Subjects
LETTERS to the editor; EXCITON theory
- Publication
Nature Materials, 2006, Vol 5, Issue 11, p861
- ISSN
1476-1122
- Publication type
Letter
- DOI
10.1038/nmat1739