Atomic transition region at the crossover between quantum dots to molecules

Bruno Ullrich, A. Antillón, Mithun Bhowmick, J. S. Wang, Haowen Xi

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


The presented investigations aim to pinpoint the crossover of lead sulfide (PbS) quantum dots (QDs) with a shrinking diameter to a molecular state. We have measured the transmittance of strongly confined PbS QDs of 2.7, 3.1, 4.7 and 4.8 nm size in the temperature range of 10-300 K. Fitting these results with the classical Fan theory revealed that the average phonon energy coincides with the reduction of the QD diameters, pointing to a limitation of coherent atom movements in strongly confined matter. The phonons vanish at QDs limited to 90 atoms corresponding to a size of 1.7 nm, which we define as the critical size for the solid-to-molecule crossover. The result is confirmed by a calculation based on the uncertainty principle.

Original languageEnglish
Article number025801
JournalPhysica Scripta
Issue number2
Publication statusPublished - Feb 2014
Externally publishedYes


  • optical properties of quantum dots
  • PbS quantum dots
  • phase transition
  • phonons in quantum dots
  • quantum dot preparation

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Atomic and Molecular Physics, and Optics
  • Mathematical Physics

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