Direct measurement of lattice dynamics and optical phonon excitation in semiconductor nanocrystals using femtosecond stimulated raman spectroscopy

Daniel C. Hannah, Kristen E. Brown, Ryan M. Young, Michael R. Wasielewski, George C. Schatz, Dick T. Co, Richard D. Schaller

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We report femtosecond stimulated Raman spectroscopy measurements of lattice dynamics in semiconductor nanocrystals and characterize longitudinal optical (LO) phonon production during confinement-enhanced, ultrafast intraband relaxation. Stimulated Raman signals from unexcited CdSe nanocrystals produce a spectral shape similar to spontaneous Raman signals. Upon photoexcitation, stimulated Raman amplitude decreases owing to experimentally resolved ultrafast phonon generation rates within the lattice. We find a ∼600 fs, particle-size-independent depletion time attributed to hole cooling, evidence of LO-to-acoustic down-conversion, and LO phonon mode softening.

Original languageEnglish
Article number107401
JournalPhysical review letters
Issue number10
Publication statusPublished - Sep 5 2013


ASJC Scopus subject areas

  • Physics and Astronomy(all)

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