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Negative diffusion of excitons in quasi-two-dimensional systems
Aleksandr A Kurilovich1, Vladimir N Mantsevich2, Aleksei V Chechkin3,4,5
1Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, 121205, Moscow, Russia.
Physical Chemistry Chemical Physics : PCCP
|December 13, 2023
Summary
Negative diffusion in semiconductors arises from excitons initially trapped and then slowly released, creating an apparent backward movement. This phenomenon is observed in quasi-two-dimensional systems and influenced by recombination and exciton interactions.
Area of Science:
- Condensed matter physics
- Semiconductor physics
- Exciton dynamics
Background:
- Negative diffusion of excitons has been experimentally observed in quasi-two-dimensional semiconductor systems.
- This phenomenon challenges conventional diffusion models and requires explanation through advanced theoretical frameworks.
Purpose of the Study:
- To explain the observed negative diffusion of excitons using mobile-immobile type models.
- To elucidate the underlying mechanisms causing the apparent backward movement of excitons.
Main Methods:
- Utilized two distinct mobile-immobile theoretical models.
- Analyzed experimental data from quasi-two-dimensional semiconductor systems.
Main Results:
- The models successfully explain negative diffusion as a result of initial exciton trapping and delayed release.
- The observed narrowing of exciton density profiles and decreased mean-squared displacement are attributed to this trapping-release mechanism.
- Negative diffusion is enhanced by increased recombination intensity and exciton-exciton binary interaction rates.
Conclusions:
- The mobile-immobile model provides a robust explanation for negative exciton diffusion in semiconductors.
- Experimental observations of negative diffusion are a consequence of exciton trapping dynamics rather than true backward diffusion.
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