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Experimental study of Efimov scenario in ultracold bosonic lithium

Experimental study of Efimov scenario in ultracold bosonic lithium. Lev Khaykovich Physics Department, Bar-Ilan University, 52900 Ramat Gan, Israel. FRISNO-11, Aussois, 28/3/2011. Outline. Experimental approach - all optical BEC of lithium Exploring Feshbach resonances on F=1 state.

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Experimental study of Efimov scenario in ultracold bosonic lithium

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  1. Experimental study of Efimov scenario in ultracold bosonic lithium Lev Khaykovich Physics Department, Bar-Ilan University, 52900 Ramat Gan, Israel FRISNO-11, Aussois, 28/3/2011

  2. Outline • Experimental approach - all optical BEC of lithium • Exploring Feshbach resonances on F=1 state. • Spontaneous spin purification. • Universal quantum states in three body domain (scattering length a is the largest length scale in the system) • Weakly bound Efimov trimers. • Log periodic behavior of three-body recombination. • Evidence of spin independent short range 3-body physics. • Mapping between the scattering length and the applied magnetic field – direct association of Feshbach molecules. • Conclusions – is the nonuniversal part of the theory nonuniversal?

  3. Experimental system: bosonic lithium Why lithium? Compared to other atomic species available for laser cooling, lithium has the smallest range of van der Waals potential: Thus it is easier to fulfill the universal physics requirement: |a| >> r0

  4. Experimental system: bosonic lithium What’s lithium? Bulk metal – light and soft Magneto-optically trapped atoms

  5. All optical BEC: optical dipole trap Direct loading of an optical dipole trap from a MOT 0 order (helping beam) +1 order (main trap) Ytterbium Fiber Laser P = 100 W N=2x106 T=300 mK w0 = 31 mm U = 2 mK main trap Q = 19.50 * The helping beam is effective only when the main beam is attenuated helping beam w0 = 40 mm N. Gross and L. Khaykovich, PRA 77, 023604 (2008)

  6. Tuning the s-wave scattering length Feshbach resonance A weakly bound state is formed for positivea – Feshbach molecule

  7. Feshbach resonances on F=1 state Theoretical prediction for Feshbach resonances S. Kokkelmans, unpublished

  8. Search for Feshbach resonances Atoms are optically pumped to F=1 state. Positions of Feshbach resonances from atom loss measurements: Narrow resonance: 845.8(7) G Wide resonance: 894.2(7) G From the whole zoo of possible resonances only two were detected.

  9. Spontaneous spin purification Spin selective measurements to identify where the atoms are. Spin-flip collisions: |F=1, mF=0> N. Gross and L. Khaykovich, PRA 77, 023604 (2008)

  10. Feshbach resonances on mF=0 state Theoretical prediction for Feshbach resonances This is not the absolute ground state!

  11. Experimental playground Absolute ground state The one but lowest Zeeman state

  12. Three-body universality: Efimovqunatum states

  13. Quantum states near two-body resonance (Efimov scenario)

  14. Universal three-body bound states even more weakly bound trimers weakly bound trimers

  15. Universal three-body bound states Position of an Efimov state is nonuniversal. It is defined by a three-body parameter.

  16. Experimental observables – Efimov resonances One atom and a dimer couple to an Efimovtrimer Three atoms couple to an Efimovtrimer Experimental observable - enhanced three-body recombination

  17. Three-body recombination Release of binding energy causes loss which probes 3-body physics.

  18. Manifistation of Efimov resonances One atom and a dimer couple to an Efimovtrimer Three atoms couple to an Efimovtrimer Enhanced three-body loss: collisions at much larger distance

  19. Experimental observables – suppressed three-body recombination There are two paths for the 3- body recombination towards deeply bound state

  20. Suppressed three-body recombination deeplyboundmolecule Two paths interfere destructively a certain scattering lengths – recombination minima.

  21. Three-body recombination theory Loss rate from a trap: K3 – 3-body loss coefficient [cm6/sec] Dimension analysis: Full treatment:

  22. Effective field theory Loss into deeply bound molecules Loss into shallow dimer Recombination minima Efimov resonances Braaten & Hammer, Phys. Rep. 428, 259 (2006)

  23. Experimental results a > 0: T= 2 – 3 mK a < 0: T= 1 – 2 mK mf = 1; Feshbach resonance ~740G. N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).

  24. Experimental results a > 0: T= 2 – 3 mK a < 0: T= 1 – 2 mK mf = 1; Feshbach resonance ~740G. mf = 0; Feshbach resonance ~895G. N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).

  25. Experimentally demonstrated Efimov features This minimum This resonance

  26. Experimentally demonstrated Efimov features Theses two resonances are related by 22.7

  27. Experimentally demonstrated Efimov features Theses two resonances are related by 22

  28. Experimentally demonstrated Efimov features This minimum This resonance This resonance

  29. Summary of the results Fitting parameters to the universal theory: • The universal factor of 22.7 is confirmed across the region of • Three-body parameter is the same (within the experimental errors) for both nuclear-spin subleves. UT prediction: a+/|a-| = 0.96(0.3) N. Gross, Z. Shotan, S. Kokkelmans and L. Khaykovich, PRL 103, 163202 (2009); PRL 105, 103203 (2010).

  30. Mapping between the scattering length And the applied magnetic field

  31. Mapping between the scattering length and the applied magnetic field Bare state (non-universal) dimer: Feshbach molecule (universal dimer):

  32. There isonly a small fraction of the wavefunction in the bound state. The size of the bound state increases. The size of the bound state isthat of a singlet potential: ~1.5 nm Universal two-body bound state Progressive contamintion by the atomic continuum “Quantum halo states”

  33. Experimental probe Loss mechanism from the trap (release of binding energy): Deeply bound molecule

  34. Mapping between the scattering length and the applied magnetic field Precise characterization of Feshbach resonances by rf-spectroscopy of universal dimers. A typical RF spectrum N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926

  35. Mapping between the scattering length and the applied magnetic field Precise characterization of Feshbach resonances by rf-spectroscopy of universal dimers. Solid (dashed) line – local (global) analysis N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926

  36. Mapping between the scattering length and the applied magnetic field Precise characterization of Feshbach resonances by rf-spectroscopy of universal dimers. Improved characterization of Li inter-atomic potentials. N. Gross, Z. Shotan, O. Machtey, S. Kokkelmans and L. Khaykovich, C.R. Physique 12, 4 (2011) ; arXiv:1009.0926

  37. Conclusions • For two different Fesbach resonances on two different nuclear-spin sublevles of the same atomic system we demonstrate: • Universal scaling factor of 22.7 across the region of . • Same positions of the Efimov features (within the experimental errors). • First experimental indication that the nonuniversal part of the universal theory – the three-body parameter – might have some “universal” properties. • New insight from Innsbruck group – for three different Feshbach resonances the Efimov features are the same!

  38. People Eindhoven University of Technology, The Netherlands Bar-Ilan University, Israel ServaasKokkelmans

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