Abstract
Many-body interactions give rise to fascinating physics such as the X-ray Fermi-edge singularity in metals, the Kondo effect in the resistance of metals with magnetic impurities and the fractional quantum Hall effect. Here we report the observation of striking many-body effects in the optical spectra of a semiconductor quantum dot interacting with a degenerate electron gas. A semiconductor quantum dot is an artificial atom, the properties of which can be controlled by means of a tunnel coupling between a metallic contact and the quantum dot. Previous studies concern mostly the regime of weak tunnel coupling, whereas here we investigate the regime of strong coupling, which markedly modifies the optical spectra. In particular we observe two many-body exciton states: Mahan and hybrid excitons. These experimental results open the route towards the observation of a tunable Kondo effect in excited states of semiconductors and are of importance for the technological implementation of quantum dots in devices for quantum information processing.
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Acknowledgements
The authors thank P. A. M. Nouwens and E. J. Geluk for their help with the sample processing. They acknowledge the stimulating environment and discussions provided by the ‘van der Waals Borrel’. This work is part of the research programme of NanoNed, which is financially supported by the NWO (The Netherlands). Other financial support comes from VICI grant no. 6631 (The Netherlands), NSF (USA) and BNNT (Ohio University, USA).
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N.A.J.M.K. and J.v.B. carried out the photoluminescence measurements. J.G.K. carried out the cross-sectional scanning tunnelling microscopy analysis. G.J.H. and R.N. grew the sample. A.O.G. carried out the theoretical calculations. N.A.J.M.K., J.v.B., A.O.G., A.Yu.S. and P.M.K. analysed and interpreted the data.
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Kleemans, N., van Bree, J., Govorov, A. et al. Many-body exciton states in self-assembled quantum dots coupled to a Fermi sea. Nature Phys 6, 534–538 (2010). https://doi.org/10.1038/nphys1673
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DOI: https://doi.org/10.1038/nphys1673
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