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World of ultracold atoms with strong interaction

World of ultracold atoms with strong interaction. Daw-Wei Wang. National Tsing-Hua University. Temperature ?. What we mean by “ultracold” ?. Why low temperature ?. Ans: To see the quantum effects !. Uncertainty principle:. (after Nature, 416 , 225 (’02)). Why strong interaction ?.

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World of ultracold atoms with strong interaction

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  1. World of ultracold atoms with strong interaction Daw-Wei Wang National Tsing-Hua University

  2. Temperature ? What we mean by “ultracold” ?

  3. Why low temperature ? Ans: To see the quantum effects ! Uncertainty principle:

  4. (after Nature, 416, 225 (’02))

  5. Why strong interaction ? P. Anderson: “Many is not more” Because interaction can make “many” to be “different” ! Example:1D interacting electrons crystalization and no fermionic excitation

  6. How to make interaction stronger ?

  7. How to reach ultracold temperature ? 1. Laser cooling ! (1997 Nobel Price) Use red detune laser + Doppler effect

  8. How to reach ultracold temperature ? 2. Evaporative cooling ! Reduce potential barrial +thermal equilibrium

  9. Typical experimental environment MIT

  10. How to do measurement ? Trapping and cooling Perturbing Releasing and measuring BEC (2001 Nobel Price)

  11. What is Bose-Einstein condensation ? When T is small enough, noninteracting bosons like to stay in the lowest energy state, i.e. BEC

  12. How about fermions in T=0 ? D(E) Fermi sea E When T-> 0, noninteracting fermions form a compact distribution in energy level.

  13. BEC and Superfluidity of bosons (after Science, 293, 843 (’01)) condensate BEC = superfluidity v repulsion Superfluid uncondensate Normal fluid Landau’s two-fluid model

  14. Phonons and interference in BEC Interference Phonon=density fluctuation (after Science 275, 637 (’97)) Matter waves ?

  15. Vortices in condensate Vortex = topological disorder E L 0 1 2 3 (after Science 292, 476 (’01)) Vortices melting, quantum Hall regime ? (after PRL 87, 190401 (’01))

  16. Spinor condensation in optical trap Na E F=2 F=1 B (see for example, cond-mat/0005001)

  17. D(E) rf-pulse Interacting fermi sea E Boson-fermion mixtures Fermions are noninteracting ! phonon fermion phonon-mediated interaction Sympathetic cooling

  18. Feshbach Resonance (i) Typical scattering: a (ii) Resonant scattering: B Molecule state

  19. Molecule and pair condensate (MIT group, PRL 92, 120403 (’04)) (JILA, after Nature 424, 47 (’03)) (Innsbruck, after Science 305, 1128 (’04))

  20. First evidence of superfluidity of fermion pairing a B

  21. other lattice Optical lattice 3D lattice 1D lattice Entanglement control

  22. Mott-Insulator transition Bose-Hubbard model n=3 superfluid n=2 n=1 (after Nature 415, 39 (’02))

  23. Fermions in optical lattice Fermi Hubbard model Superfluidity of fermion pairing in lattice is also realized.

  24. wire Transport in 1D waveguide wave guide Interference ? Finite temperature + semiconductor technique

  25. (2) Atoms with large magnetic moment (1) Heteronuclear molecules Small moment Dipoles in nature: (a) Direct molecules p~ 1-5 D (b) But difficult to be cooled But it is now ready to go ! (Stuhler etc.) (Doyle, Meijer, DeMille etc.)

  26. Condensate (superfluid) Tc~700 nK

  27. (2) Atoms with large magnetic moment (1) Heteronuclear molecules Small moment Cold dipolar atoms/molecules (a) Direct molecules p~ 1-5 D (b) But difficult to be cooled But it is now ready to go ! (Stuhler etc.) (Doyle, Meijer, DeMille etc.)

  28. Condensate (superfluid) Tc~700 nK

  29. Interdisciplinary field Traditional AMO Precise measurement Cosmology Ultracold atoms Quantum Information Nonlinear Physics Soft-matter/ chemistry Condensed matter

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