Origin of the Stokes shift: a geometrical model of exciton spectra in 2D semiconductors

Fang Yang, M. Wilkinson, E. J. Austin, K. P. O'Donnell

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We consider the optical absorption and emission spectra of excitons in two-dimensional semiconductors disordered through interface fluctuations. These spectra show a universal behavior exemplified by the fact that the offset of the spectral peaks (the Stokes shift) is proportinal to their linewidths over a range of at least 2 orders of magnitude. We introduce a topographical theory of the exciton spectra which models such behavior in terms of statistical properties of a Gaussian random function. The coefficient of proportionality between the Stokes shift and the exciton absorption linewidth is found to be γ=2/ 6π ln2 =0.553 by analysis and 0.6 by experiment.

Original languageEnglish
Pages (from-to)323-326
Number of pages4
JournalPhysical Review Letters
Issue number3
Publication statusPublished - 18 Jan 1993


  • optical absorption
  • stokes shift
  • linewidth

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