Exciton polarizability in semiconductor nanocrystals

Feng Wang, Jie Shan, Mohammad A. Islam, Irving P. Herman, Mischa Bonn, Tony F. Heinz

Research output: Contribution to journalArticlepeer-review

124 Scopus citations

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 (1-2.5nm) 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 1043 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.

Original languageEnglish (US)
Pages (from-to)861-864
Number of pages4
JournalNature Materials
Volume5
Issue number11
DOIs
StatePublished - Nov 9 2006

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint Dive into the research topics of 'Exciton polarizability in semiconductor nanocrystals'. Together they form a unique fingerprint.

Cite this