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Updated: Mar 5, 2026
08:04
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
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Bose-Einstein condensation and indirect excitons: a review.
Monique Combescot1, Roland Combescot2,3, François Dubin1
1Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 place Jussieu, 75005 Paris, France.
Summary
Bose-Einstein condensation (BEC) of semiconductor excitons is reviewed, focusing on dark condensates. Experiments confirm that indirect excitons form a spatially coherent, essentially dark condensate at low temperatures.
Area of Science:
- Condensed matter physics
- Quantum optics
- Semiconductor physics
Background:
- Bose-Einstein condensation (BEC) is a state of matter formed by bosons cooled to near absolute zero.
- Semiconductor excitons, quasi-particles formed by electrons and holes, have been explored for BEC.
- Recent theoretical insights suggest exciton condensates are inherently dark due to ground state properties.
Purpose of the Study:
- To review theoretical and experimental progress on Bose-Einstein condensation of semiconductor excitons.
- To elucidate the 'dark' nature of exciton condensates and its implications.
- To present experimental evidence supporting the theoretical understanding of dark exciton BEC.
Main Methods:
- Theoretical analysis of Bose-Einstein condensation for elementary and composite bosons.
- Investigation of exciton spin structure and light-coupling properties.
- Experimental techniques including optical creation and photoluminescence detection of indirect excitons.
- Analysis of exciton thermalization, density estimation, and spatial coherence.
Main Results:
- Ground-state excitons are dark, meaning the exciton Bose-Einstein condensate is not directly coupled to light in the dilute regime.
- At higher densities, the exciton condensate transitions from fully dark to 'gray', possessing a coherent bright component.
- Experiments demonstrate the formation of a macroscopic, spatially coherent, and essentially dark exciton Bose-Einstein condensate in fragmented rings of indirect excitons at sub-Kelvin temperatures.
Conclusions:
- The theoretical understanding of dark exciton Bose-Einstein condensation is experimentally supported.
- Indirect excitons provide a viable system for studying BEC properties, including spatial coherence.
- The transition from dark to gray condensates offers new avenues for exploring quantum phenomena in semiconductors.
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