Radiative Auger process in the single-photon limit


In a multi-electron atom, an excited electron can decay by emitting a photon. Typically, the leftover electrons are in their ground state. In a radiative Auger process, the leftover electrons are in an excited state and a redshifted photon is created1,2,3,4. In a semiconductor quantum dot, radiative Auger is predicted for charged excitons5. Here we report the observation of radiative Auger on trions in single quantum dots. For a trion, a photon is created on electron–hole recombination, leaving behind a single electron. The radiative Auger process promotes this additional (Auger) electron to a higher shell of the quantum dot. We show that the radiative Auger effect is a powerful probe of this single electron: the energy separations between the resonance fluorescence and the radiative Auger emission directly measure the single-particle splittings of the electronic states in the quantum dot with high precision. In semiconductors, these single-particle splittings are otherwise hard to access by optical means as particles are excited typically in pairs, as excitons. After the radiative Auger emission, the Auger carrier relaxes back to the lowest shell. Going beyond the original theoretical proposals, we show how applying quantum optics techniques to the radiative Auger photons gives access to the single-electron dynamics, notably relaxation and tunnelling. This is also hard to access by optical means: even for quasi-resonant p-shell excitation, electron relaxation takes place in the presence of a hole, complicating the relaxation dynamics. The radiative Auger effect can be exploited in other semiconductor nanostructures and quantum emitters in the solid state to determine the energy levels and the dynamics of a single carrier.

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Fig. 1: Observation of a radiative Auger process on a single QD.
Fig. 2: Magnetic field dispersion of the radiative Auger emission.
Fig. 3: Time-resolved correlation measurements.

Data availability

The data that support this work are available from the corresponding author upon reasonable request.

Code availability

The code that has been used for this work is available from the corresponding author upon reasonable request.


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We thank P. Treutlein for fruitful discussions. M.C.L., C.S. and R.J.W. acknowledge financial support from NCCR QSIT and from SNF project number 200020_156637. L.Z. received funding from the European Union Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie grant agreement number 721394 (4PHOTON). A.J. acknowledges support from the European Unions Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 840453 (HiFig). J.R., A.L. and A.D.W. gratefully acknowledge financial support from the grants DFH/UFA CDFA05-06, DFG TRR160, DFG project 383065199, and BMBF Q.Link.X 16KIS0867. L.M. and P.L. gratefully acknowledge financial support from the Danish National Research Foundation (Center of Excellence Hy-Q, grant number DNRF139) and the European Research Council (ERC Advanced Grant SCALE).

Author information




M.C.L., C.S., L.Z., G.N.N. and A.J. performed the experiments. J.R., A.D.W. and A.L. grew the samples. C.S., M.C.L. and L.M. fabricated the different samples. M.C.L., L.Z., P.L. and A.L. designed the samples. M.C.L., C.S., L.Z. and R.J.W. analysed the data. M.C.L. developed the theory of the radiative Auger process. A.J., M.C.L. and C.S. developed the theory for the time-resolved measurements. M.C.L., R.J.W. and C.S. developed the theory for the magnetic field dispersion. M.C.L. and R.J.W. initiated the project and wrote the manuscript with input from all the authors.

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Correspondence to Matthias C. Löbl.

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Peer review information Nature Nanotechnology thanks Val Zwiller and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–6, tables 1–3 and refs. 1–19.

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Löbl, M.C., Spinnler, C., Javadi, A. et al. Radiative Auger process in the single-photon limit. Nat. Nanotechnol. 15, 558–562 (2020). https://doi.org/10.1038/s41565-020-0697-2

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