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Observation of an Efimov spectrum in an atomic system

Observation of an Efimov spectrum in an atomic system. Matteo Zaccanti LENS, University of Florence. Universality in 2- 3-(4)-body systems. V(r). Point-like particles. If | a |  r 0. a >0. Low energy and | a |>> r 0 : universal regime.

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Observation of an Efimov spectrum in an atomic system

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  1. Observation of an Efimov spectrum in an atomic system Matteo Zaccanti LENS, University of Florence

  2. Universality in 2- 3-(4)-body systems V(r) Point-like particles If |a|r0 a >0 Low energy and |a|>>r0 : universal regime Scattering doesn’t depend on the microscopic V(r)

  3. Universality in 2- 3-(4)-body systems Efimov effect ? |a|∞ |a| r0 See B&H review 2006

  4. Universality in 2- 3-(4)-body systems No additional 4-body parameter Each Efimov state accompanied by two 4B states von Stecher et al, arXiv:0810.3876

  5. To summarize… Ultracold atomic gases + Feshbach resonances Ideal test bed for Efimov physics!!! To explore Efimov scenario: • Tunable a over wide range • Low collision energy Kraemer et al.,Nature 440, 315 (2006) Knoop et al., Nat. Phys. 5, 227 (2009) Ottenstein et al., PRL 101, 203202 (2008) Ferlaino et al. PRL 102, 140401 (2009) Barontini et al.,arXiv:0901.4584

  6. To take in mind… Efimov scenario r0 =0 Real world r0 ~lVdW Coincidence only as |a|>>r0 Expected deviations for the deepest states of the ladder Additional 3-body parameter is needed!!! (Unknown location of the first Efimov feature)

  7. Efimov scenario & 3-body observables Universal relations between a-n a+n and a*n

  8. Efimov physics in 39K • Small background scattering length: abg=-29 a0 D’Errico et al. NJP 9, 223 (2007) • Broad Feshbach resonances: good control on a (B) Roati et al, PRL 99, 010403 (2007) Fattori et al, PRL 101, 190405 (2008) • no narrow resonances • connection between a >0 and a <0 via universal region

  9. Efimov physics in 39K 3-body recombination vs a Explored: [-300; -8000] a0 [+20;+25000] a0

  10. Efimov physics in 39K Presence of two trimer states very close to Efimov scenario!!!

  11. Efimov physics in 39K a > 0 Two recombination minima

  12. Efimov physics in 39K … and associated 4-body feature(s) a < 0 One Efimov resonance…

  13. Efimov physics in 39K … close to the AD resonances (unexpected) a > 0 Two recombination maxima…

  14. Efimov physics in 39K • enhanced AD scattering cross section Where are the dimers? Three body processes! K3 enhancement due to nl enhancement What’s going on?

  15. Efimov physics in 39K Usually, the three-body process causes nl =3

  16. Efimov physics in 39K Similar in BEC of 87Rb above critical opacity …but if AD cross section is large it can be nl >>3!!!

  17. Efimov physics in 39K Idea confirmed from a simple model for AD collisions…

  18. Efimov physics in 39K Similar mechanism at the other feature

  19. Ideal vs real world: a comparison Larger spacing Simultaneous fit gives: s0=0.956(18)

  20. Ideal vs real world: a comparison Consistent with recent theo. predictions Hammer et al., PRA 75 032715 (2007) Thøgersten et al., PRA 78 020501 (2008) Platter et al., PRA 79 022702 (2009) D’incao et al., J. Phys. B 42 044016 (2009)

  21. Outlook & Conclusions • Different FRs: other Efimov spectra on the same atomic system. • Further investigations: AD scattering, 4-body features, association of Efimov trimers, low dimensions… • Universality vs short-range effects

  22. Thank you for your attention!

  23. Efimov scenario & 3-body observables atom-dimer scattering 3-body recombination

  24. Efimov scenario & 3-body observables 3-body recombination particle-dimer scattering

  25. Efimov physics in 39K: experiment & analysis Note that inelastic AD scattering causes an increase of only nl =3->nl =4

  26. Efimov physics in 39K: experiment & analysis Simple considerations allow to estimate them: pe = 1- exp(-n lsAD) pi(0) = 1- exp(-bAD/(v0sAD)) After kM ED<ETrap kS such that pi(kS)=1 pe= prob. for D of elastic AD collision before leaving the trap Pi(k)= prob. for D of inelastic AD collision before the k-th el. coll Analytic exp. available in the low-energy limit for sAD and bAD

  27. Efimov physics in 39K: experiment & analysis UT/30 UT …and compare exp. with K3=anl You can include all possible events, extract nl

  28. Outline • Universality in few-body systems • Efimov’s scenario & 3-body observables • Efimov’s physics in 39K • Ideal vs real world: a comparison • Outlook & perspectives

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