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Hybridization of electronic states in quantum dots through photon emission

Abstract

The self-assembly of semiconductor quantum dots has opened up new opportunities in photonics. Quantum dots are usually described as ‘artificial atoms’, because electron and hole confinement gives rise to discrete energy levels. This picture can be justified from the shell structure observed as a quantum dot is filled either with excitons1 (bound electron–hole pairs) or with electrons2. The discrete energy levels have been most spectacularly exploited in single photon sources that use a single quantum dot as emitter3,4,5,6. At low temperatures, the artificial atom picture is strengthened by the long coherence times of excitons in quantum dots7,8,9, motivating the application of quantum dots in quantum optics and quantum information processing. In this context, excitons in quantum dots have already been manipulated coherently10,11,12. We show here that quantum dots can also possess electronic states that go far beyond the artificial atom model. These states are a coherent hybridization of localized quantum dot states and extended continuum states: they have no analogue in atomic physics. The states are generated by the emission of a photon from a quantum dot. We show how a new version of the Anderson model that describes interactions between localized and extended states can account for the observed hybridization.

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Figure 1: Photoluminescence from charged excitons.
Figure 2: Photoluminescence energy versus magnetic field for the X3- exciton.
Figure 3: Quantum dot level diagrams in the artificial atom model.
Figure 4: Hybridization in the final state after photon emission.
Figure 5: A comparison of the results from the Anderson hamiltonian model with the experiment for the X3- exciton.

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Acknowledgements

We acknowledge discussions with A. Rosch and J. von Delft. This work was funded by the DFG, EPSRC and The Royal Society.

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Correspondence to Richard J. Warburton.

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The authors declare that they have no competing financial interests.

Supplementary information

41586_2004_BFnature02109_MOESM1_ESM.jpg

Supplementary Figure 1: Photoluminescence (PL) versus gate voltage (Vg) from a single quantum dot at 4.2 K and at zero magnetic field (a), and at 9 T (b). (JPG 67 kb)

Supplementary Figure 1 Legend (PDF 25 kb)

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Karrai, K., Warburton, R., Schulhauser, C. et al. Hybridization of electronic states in quantum dots through photon emission. Nature 427, 135–138 (2004). https://doi.org/10.1038/nature02109

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