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Single Mn atom in CdTe / ZnTe quantum dot as an optical quantum memory

Single Mn atom in CdTe / ZnTe quantum dot as an optical quantum memory. T. Smoleński 1 , M. Goryca 1,2 , T. Kazimierczuk 1 , J. A. Gaj 1 , P. Płochocka 2 , M. Potemski 2 ,P. Wojnar 3 , P. Kossacki 1,2. Institute of Experimental Physics , University of Warsaw

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Single Mn atom in CdTe / ZnTe quantum dot as an optical quantum memory

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  1. Single Mn atom inCdTe/ZnTe quantum dot as an optical quantum memory T. Smoleński1, M. Goryca1,2, T. Kazimierczuk1 , J. A. Gaj1, P. Płochocka2, M. Potemski2,P. Wojnar3, P. Kossacki1,2 • Institute of ExperimentalPhysics, University of Warsaw • Grenoble High Magnetic Field Laboratory • Institue of Physics, PolishAcademy of Sciences

  2. Outline • Introduction – what a quantum dot (QD) is? • Samples – how to observe a single magnetic atom • Experiment 1. Opticalreading of information on the Mn spin state 2. Opticalwriting and storage of information • Conclusion

  3. Quantum dots • Nanostructures, made of two semiconductors with different energy gaps • Innermaterial, withsmall energy gap CdTe ECdTe EZnTe 10 nm ZnTe • Outermaterial, withwide energy gap

  4. Excitonin QD • Jz = ±1/2 • Jz = ±3/2 • +e • -e Exciton X • Twotypes of carriers: electronsand holes • 4 possible spin states of X • Jz= -1 • Jz= +2 • Jz= -2 • Jz= +1

  5. Excitonin QD • Twotypes of carriers: electronsand holes • 4 possible spin states of X • Jz= -1 • Jz= +2 • Jz= -2 • Jz= +1 • Theway to observe single QDs: photoluminescencemeasurements !

  6. QD with a single Mn ion Energy • Single Mn ion: S = 5/2, L = 0 • Mn has 6 possible spin stateswith 6 differentSzvalues exchangeinteraction between Mn and X Mn

  7. Samples CdTe(formationlayer) • How to make QDs? We can do itusing MBE method. ZnTe • In an appropriate moment we opentheeffusivecellwith Mn atoms for a short time. ZnTe CdTe(buffer) GaAs(substrate) • Number of Mn ionsin a • single QD ~ 1

  8. Experimental setup • How to observe a single QD? Tunabledye laser T=1.5K Modulators Criostatwith microscope Pol λ/4 Monochromator with CCD camera and avalanchephotodiode

  9. Optical QD excitation • How to introduce spin polarizedexcitons to QD with single Mn ion? • We shoulduse … another QD without Mn ion! • Lightshould be circularlypolarized (i.e. s-) Mn

  10. Photoluminescence spectrum • Excitationwithunpolarizedlight = unoriented Mn spin Mn

  11. Photoluminescence spectrum (2) s+ photoluminescence (arb. u.) energy (eV) energy (eV) • Excitationwithcircularlypolarizedlight = we observe Mn spin orientation!

  12. Whatisthestorage time? I • Excitation σ+ t • Steady state

  13. Whatisthestorage time? I σ+ σ- • Excitation t • Steady state

  14. Whatisthestorage time? I σ+ σ- • Excitation t • Steady state I • Signal on APD t

  15. Whatisthestorage time? I σ+ σ- • Excitation t • Steady state I • Signal on APD t

  16. Whatisthestorage time? I σ+ σ- • Excitation t • Steady state I • Signal on APD t

  17. Storage time determination I σ+ σ- • Excitationscheme t Storage time ~ 0.4 ms

  18. Conclusion • We demonstrated optical writing and reading of information on the spin state of a single Mn ion embedded in a CdTe/ZnTe QD • We shown, thatsingle magnetic atom in a QDis a spin memory with optical writing and readout of information, storage time ~1ms

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