Effects of collective excitations and scatterings in quantum well intersubband transitions

Cun-Zheng Ning, J. Li

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


Quantum well intersubband transitions display some of the most interesting many-body effects including various collective excitations, such as intersubband plasmon and Fermi-edge singularity (repellon). To describe these various excitations and to study the effects of scatterings on the intersubband lineshape, we have performed a systematic microscopic theoretical investigation of intersubband transitions. The theory leads to a set of intersubband semiconductor Bloch equations (ISBEs) at the first order of Coulomb interaction. The extension to include the second order Coulomb interaction and LO-phonon interaction leads to optical dephasing or linewidth broadening. Using this theory, we have studied systematically the interplay of collective excitations in quantum well intersubband transitions. Our results show that such interplay leads to dramatic changes in spectral features, such as absorption peak positions and lineshape, compared with a free-particle theory. We will also show that the typical usage of the dephasing rate approximation is generally invalid for intersubband transitions. There is a strong cancellation effects between the in- (off-diagonal) and out(diagonal) scattering terms at the second order and the out-scattering alone overestimates the linewidth significantly. Such a cancellation is much stronger for intersubband transitions than for interband case, because of the much smaller inhomogeneous broadening in the intersubband case. We also show that there is a cancellation of electron-electron and electron-phonon scatterings in their contributions to the linewidth. Finally we will show that our theory agrees very well with recent infrared absorption experiments.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsK.T. Tsen, J.J. Song, H. Jiang
Number of pages15
StatePublished - 2004
Externally publishedYes
EventUltrafast Phenomena in Semiconductors and Nanostructure Materials VIII - San Jose, CA, United States
Duration: Jan 26 2004Jan 29 2004


OtherUltrafast Phenomena in Semiconductors and Nanostructure Materials VIII
Country/TerritoryUnited States
CitySan Jose, CA


  • Collective excitation
  • Electron scattering
  • Intersubband transition
  • Linewidth
  • Many-body effects
  • Nanostructures
  • Phonon scattering
  • Quantum wells

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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