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Subnanosecond spectral diffusion of a single quantum dot in a nanowire

Subnanosecond spectral diffusion of a single quantum dot in a nanowire. G. Sallen, A. Tribu, T. Aichele*, R. André, L. Besombes, C. Bougerol, M. Richard, S. Tatarenko, K. Kheng, and J.-Ph. Poizat. CEA/CNRS/UJF joint team "Nanophysics and semi-conductors"

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Subnanosecond spectral diffusion of a single quantum dot in a nanowire

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  1. Subnanosecond spectral diffusion of a single quantum dot in a nanowire G. Sallen, A. Tribu, T. Aichele*, R. André, L. Besombes, C. Bougerol, M. Richard, S. Tatarenko, K. Kheng, and J.-Ph. Poizat CEA/CNRS/UJF joint team "Nanophysics and semi-conductors" Institut Néel and INAC, Grenoble, France * Present address :Physics Institute, Humboldt University, Berlin, Germany www.neel.cnrs.fr

  2. Spectral diffusion Random spectral jumps of a narrow line as a result of fluctuating environment Described by two parameters S : diffusion amplitude td : diffusion time S Std < h : motional narrowing (dephasing) Lorentzian lineshape Std > h : wandering line : Gaussian lineshape A. Berthelot et al, Nat Phys (2006) www.neel.cnrs.fr

  3. Spectral diffusion of a single emitter Standard method : Record spectra time serie Time resolution > 1 ms Alternative methods : * Resonant excitation of a fluctuating line, photon correlation on the luminescence. Time resolution > 1µs Zambusch et al, PRL (1993) * Photon-correlation Fourier spectroscopy. Time resolution > 20 µs Coolen et al, PRL (2008) Besombes et al, PRB (2002)

  4. Our method Photon correlations on parts of the line : L side H side t t t Best time resolution : 90 ps

  5. Results a) Whole line auto- correlation L side H side L side Auto- correlation b) L- H cross- correlation t t t Slow detectors : time resolution = 800ps

  6. Robustness with respect to energy slot size Cross-correlation The cross-correlation does not depend on the size of the energy slots

  7. Robustness with respect to energy separation Cross-correlation The probability of a spectral jump does not depend on its amplitude

  8. CX X XX ~ 400 nm ~ 10 nm Our sample Single CdSe quantum dot inserted in a ZnSe nanowire Lifetimes : tX = 500 ps tCX = 650 ps tCX = 450 ps Antibunching @ T=220K : Tribu et al, NanoLett (2008) Photon correlation spectroscopy : Sallen et al, PRB (2009)

  9. Diffusion rate vs excitation power sat PCX Spectral diffusion of the CX line (T=4K, T=10K) T=10K g10K/g4K => Etrap= 1.1 meV CX to X diffusion rate T=4K Linewidth = cste => Single charge exploring the traps

  10. Spectral diffusion possible scenario ZnSe CdSe ZnSe 10 nm ~3 nm Conduction band 1.1 meV QD

  11. Correlated spectral diffusion XX XX CX X X The sign of the energy shift induced by the fluctuating environment is the same on X and XX. Fast detectors : time resolution= 90ps

  12. Conclusions * Simple and robust method to measure spectral diffusion with 90 ps resolution (4 orders of magnitude improvement compared to best existing resolution). * Spectral duration time gives the under which there is no spectral diffusion. * Opens new possibilities for the investigation of the very local environnement of single emitters.

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