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Electrical control and optical probing of a single Mn atom in a quantum dot

Electrical control and optical probing of a single Mn atom in a quantum dot . J. Fernández-Rossier. OPLDS 2007. DOWNLOAD FROM: www.ua.es/personal/jfrossier/. Electrical control and optical probing of a single Mn atom in a quantum dot . J. Fernández-Rossier. Department of Applied Physics,

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Electrical control and optical probing of a single Mn atom in a quantum dot

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  1. Electrical control and optical probing of a single Mn atom in a quantum dot J. Fernández-Rossier OPLDS 2007 DOWNLOAD FROM: www.ua.es/personal/jfrossier/

  2. Electrical control and optical probing of a single Mn atom in a quantum dot J. Fernández-Rossier Department of Applied Physics, U. Alicante SPAIN CdTe QD single Mn Vb Optical probing of 1 Mn spin Gating single Mn spin with 1 electron accuracy OPLDS 2007 DOWNLOAD FROM: www.ua.es/personal/jfrossier/

  3. Collaborators and papers • Collaborators: • R. Aguado, L. Brey (ICMM, CSIC) • Y. Leger, L. Besombes, Y. Maingault, H. Mariette • JFR and L. Brey, PRL 93, 1172001 (04) • JFR, PRB73, 045301 (06) • Y. Leger, L. Besombes, JFR, Y Maingault, H, Mariette, PRL 97,07401 (06) • JFR and R. Aguado, PRL98, 106805 (07)

  4. Outline: • What we understand: • Mn-carrier exchange interactions • Spin orbit, confinement and anisotropy • Difference between electrons and holes • Effect of number of carriers on PL • excitons, • biexcitons • trions • Effect of number of Mn atoms on PL • Effect of number of carriers on magnetism • Single Electron transport • Theory work in progress: • Control of single Mn spin using laser pulses • Mn spin decoherence due to charge fluctuations • Mn-Mn entanglement: production and detection

  5. (Incomplete list of) Experimental work: • Many-Mn dot. PL • Many-Mn dot: time resolved (02) • Single-Mn Dot PL (04) • Single-Mn Dot: biexcitons (04) • Single-Mn Dot: trions (charge control) (06) • Coulomb Blockade: GaMnAs (06) • Resonant transport (06) • G. Bacher, L. Besombes, Dorozkhin,Forchel, Furdyna, Gamelin, P. Kossacki, Kossut, Maksimov, H. Mariette, Mollenkamp, Norris, L. M. Smith, Seufert, Wunderlich Previous Work and challenges • (Incomplete list of) Theory work: • DMS (Bulk, QW) 80-90 • P Hawrylack (93) • Rashba, Efros (01) (Transport in Single Mn-doped dot) • A. Govorov (04): (optical reading single Mn, Optical control) • Kyrichenko, Kossut (2004) (hole states, anisotropy) • JFR-Brey (04) (magnetism) • P. Hawrylack, Qu, Climente,Abolfath, Zutic (04-07) (Coulomb) • M. Flatte (Single Mn control) (2006) • Qu, Vasilopoulos • Experimental challenges: • Time resolved dynamics of single Mn spin • 2 Mn dot • Nanowires • Transport through single self-assembled CdTe:Mn dot

  6. Summary of Experimental Results: single Dot PL spectrocopy Exciton NON MAGNETIC CdTe QD Biexciton Trion L. Besombes et al., Phys. Rev. B 65, 121314 (2002) 6 lines 6 lines 11 lines CdTe QD +1 Mn Y. Léger et al., PRL 97,07401 (06)

  7. Mn carrier exchange interactions • JFR and L. Sham, PRB B64, 235323 (01) • JFR and L. Brey, PRL 93, 1172001 (04) • JFR, PRB73, 045301 (06)

  8. Basic Notions • Mn in CdTe: • Mn replaces Cd: Mn2+ • Mn2+ S=5/2, L=0, 2S+1=6 Cd: 3d10 4s2 Mn: 3d5 4s2 SPIN DENSITY • EXCHANGE INTERACTIONS: • Mn - CB electron • Mn - VB hole • Mn-Mn: Short range AF QD affects both SYMMETRY and Amplitude

  9. QD + 1 Mn: optical ground states vs CHARGE S=2 5 7 S=3 2 2 Q=0 Q=-1 Q=+1 2 2 S=5/2 2 2 n=p=0 n=0,p=1 n=1,p=0 # of states=6(=2S+1) # of states=12 # of states=12 G. S. S=3 G. S. Mn Heisenberg Coupled to electron Mn Ising Coupled to hole Free Mn, S=5/2

  10. EXCITON-ground transtions. Q=0 Experiment Exciton States c Exciton State d a b e f f c d e b a Ground State Full Shell 6 “ground” states

  11. Why hole-Mn coupling is anisotropic? Strong Spin-Orbit correlates spin and orbital moments Orbital orthogonality Spin exchange can not flip orbital part ... But LH-HH mixing permits some spin exchange.

  12. 3. Diagonalize exactly Mn+carrier Hamiltonian 4. Compute PL • Obtain single particle states from kp model • Calculate spin matrix elements General Theory (1) VB holes F. V. Kyrychenko and J. Kossut, PRB 70, 205317 (2004) Lowest Level only Depend on LH-HH mixing Depending on dot: Ising, anisotropic Heisenberg JFR, PRB73, 045301 (06)

  13. 3. Diagonalize exactly Mn+carrier Hamiltonian 4. Compute PL • Obtain single particle states from kp model • Calculate spin matrix elements General Theory (2) CB electrons NO Spin Orbit -> Isotropic Heisenberg Complete exciton+Mn Hamiltonian JFR, PRB73, 045301 (06)

  14. 3. Diagonalize exactly Mn+carrier Hamiltonian 4. Compute PL • Obtain single particle states from kp model • Calculate spin matrix elements General Theory (3) Diagonalize Mn and exciton+Mn • Photon emission Rates: • Energy conservation • Optical Selection Rule • Mn conservation selection Rule(Mn Spin Frank Condon) Height of the peaks=Occupation emitting state * rate JFR, PRB73, 045301 (06)

  15. Other dots EXP Y. Léger et al. PRL 95, 047403 (05) WE UNDERSTAND e+h+Mn THEORY JFR, PRB73, 045301 (06)

  16. Effect of number of carriers on PL • Y. Leger, L. Besombes, JFR, Y Maingault, H, Mariette, PRL 97,07401 (06) • JFR, R. Aguado, PRL98, 106805 (2007)

  17. QD + 1 Mn: optical ground states for CHARGE= ±2 S=5/2 6 Q=+2 Q=-2 n=0,p=2 n=2,p=0 # of states=6 # of states=6 G. S. G. S. S=5/2 Mn spin with easy axis. Free Mn spin

  18. Fine structure for 2 holes: perturbation theory Mn spin with easy axis. =0.1 meV

  19. BIEXCITON-exciton states. Biexciton Biexciton States Full Shell Full Shell Exciton Exciton states

  20. a b TRION states (1 Mn dot). Q=-1 12 Trion States Exp. b a Full Shell a b S=2 S=2 S=3 S=3 12 “ground” states

  21. a b Lineshape: spin Frank Condon factors Clebsch-Gordan Charged Ground State Trion State x Forbidden transition: S=2 S=3

  22. Electrically Tunable single atom magnet Q=-1 Q=0 Q=+1 Q=+2 ST Mz 1 2 3 4 5 6 Ising Heisenberg MZ2 Free HH S=2 S=3

  23. Effect of number of Mn atoms on PL Single Exciton spectroscopy of semimagnetic QDJFR, PRB 73, 045301 (2006)

  24. PL from CdTe QD+ 2 Mn 11 PEAKS Lowest energy X+Mn state: J1=J2 Exciton Polaron J1=2J2 Exciton induced Mn-Mn coupling J1=10J2 JFR, PRB 73, 045301 (06)

  25. PL from CdTe QD+ 3 Mn 16 PEAKS Exciton Polaron Exciton induced Mn-Mn coupling JFR, PRB 73, 045301 (06)

  26. Control of single Mn spin using laser pulses A. O. Govorov and A. V. Kalameitsev, PRB71, 035338 (2005)

  27. Optical Manipulation Exchange Emission Absorption Mn precession involves Ground State Coherence Mz Mz x Mx Mz

  28. Detection Excitation with laser pulse Detection of collective Mn Precession: Faraday Long lived Mn precession S. A. Crooker et al., PRB 56, 7574 (’97)

  29. Spin coherence and Optical coherence Purely Coherent Evolution due to laser pulse Before pulse: Only ground state coherence and occupation Before pulse: Only ground state coherence and occupation

  30. Mn spin: decoherence and relaxation due to Charge fluctuations JFR, R. Aguado, PRL98, 106805 (2007)

  31. Mn spin relaxation Spin relaxation: charged dot Mn spin relaxation: neutral QD • Dominated by Mn-Mn coupling • T1 up to 1ms in diluted samples • Probably larger in dots • Spin= Mn+ fermion • Most likely very large T1 for Mn+ holes Energy permitted SPIN FORBIDDEN JFR, R. Aguado, Phys. Stat. Sol. (c) 3, 3734 (2006) From T. Dietl et al., PRL 74, 474 (95)

  32. Master equation: charge fluctuations induce decoherence Density matrix (Vg, Vb) MASTER EQUATION Scattering Rates JFR, R. Aguado, PRL98, 106805 (2007)

  33. Master equation: charge fluctuations induce decoherence Coherent evolution Charge fluctuation induced decoherence JFR, R. Aguado, PRL98, 106805 (2007)

  34. Outlook Quantum dot with a resident spin • Usual goals (1 q-bit): • 1 qubit: initialize, manipulate, read • 2 qubits: entangle • Do it faster than decoherence Single Mn. S = 5/2 How can we use it as 1 or 2 qbits? Manipulate? Read? Initialize? Scale this up? Decoherence? Mn spin dynamics: DEPENDS A LOT ON CHARGE

  35. Outlook: Single TM atom systems Vb CdTe QD +1 Mn H.C. Manoharan,C.P. Lutz and D. Eigler, Nature 403, 512 (2000) Y. Léger, et al. PRL 97,07401 (06)

  36. IMPLICATIONS AND CONCLUSIONS Vb X- X X2 CdTe QD +1 Mn EVEN EVEN ODD • Spin orbit interaction: crucial in Mn-hole coupling • Anisotropy: good to read and manipulate. • 1 Mn in CdTe QD: Electrically tunable quantum magnet • Laser pulses: afford time control of S • QD: interface between Mn and macro-world • Y. Leger, L. Besombes, JFR, Y Maingault, H, Mariette, PRL 97,07401 (06) • JFR, R. Aguado, PRL98, 106805 (2007) DOWNLOAD THIS TALK :www.ua.es/personal/jfrossier/

  37. Thanks for your attention and see you in Alicante

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