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Localization of optically excited states by self-trapping
Michael Rohlfing1, Johannes Pollmann
1Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany.
Physical Review Letters
|May 15, 2002
Summary
Self-trapping localizes surface excitons at the Si(111)-(2x1) surface. This phenomenon, driven by electronic-geometric interplay and structural relaxation, causes temperature-dependent optical linewidths and a large Stokes shift in luminescence.
Area of Science:
- Surface science
- Solid-state physics
- Materials science
Background:
- Surface excitons are crucial for understanding optical properties of semiconductor surfaces.
- The Si(111)-(2x1) surface is a model system for studying surface electronic phenomena.
Purpose of the Study:
- To investigate the localization mechanism of surface excitons at the Si(111)-(2x1) surface.
- To elucidate the role of self-trapping and structural relaxation in the optical response.
Main Methods:
- Theoretical analysis of electronic and geometric degrees of freedom.
- Modeling of exciton dynamics and optical properties.
Main Results:
- Surface exciton localization is attributed to self-trapping via structural relaxation in the excited state.
- A characteristic temperature-dependent linewidth of the optical response is observed.
- A significant Stokes shift in luminescence is linked to the self-trapping mechanism.
Conclusions:
- Self-trapping, driven by the interplay of electronic and geometric factors, is key to exciton localization.
- A single dominant geometric deformation mode, coupled with internal charge transfer, significantly contributes to self-trapping.