World of ultracold atoms with strong interaction

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World of ultracold atoms with strong interaction
Daw-Wei Wang
National Tsing-Hua University
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Temperature ?
What we mean by ultracold ?
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Why low temperature ?
Ans To see the quantum effects !
Uncertainty principle
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(after Nature, 416, 225 (02))
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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
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How to make interaction stronger ?
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How to reach ultracold temperature ?
1. Laser cooling ! (1997 Nobel Price)
Use red detune laser Doppler effect
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How to reach ultracold temperature ?
2. Evaporative cooling !
Reduce potential barrial thermal equilibrium
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Typical experimental environment
MIT
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How to do measurement ?
Trapping and cooling
Perturbing
Releasing and measuring
BEC
(2001 Nobel Price)
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What is Bose-Einstein condensation ?
When T is small enough, noninteracting
bosons like to stay in the lowest energy state,
i.e. BEC
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How about fermions in T0 ?
D(E)
Fermi sea
E
When T-gt 0, noninteracting fermions form a
compact distribution in energy level.
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BEC and Superfluidity of bosons
(after Science, 293, 843 (01))
condensate
BEC superfluidity
v
repulsion
Superfluid
uncondensate
Normal fluid
Landaus two-fluid model
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Phonons and interference in BEC
Interference
Phonondensity fluctuation
(after Science 275, 637 (97))
Matter waves ?
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Vortices in condensate
Vortex topological disorder
E
L
1
3
2
0
(after Science 292, 476 (01))
Vortices melting, quantum Hall regime ?
(after PRL 87, 190401 (01))
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Spinor condensation in optical trap
Na
E
F2
F1
B
(see for example, cond-mat/0005001)
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Boson-fermion mixtures
Fermions are noninteracting !
phonon
fermion
phonon-mediated interaction
Sympathetic cooling
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Feshbach Resonance
(i) Typical scattering
a
(ii) Resonant scattering
B
Molecule state
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Molecule and pair condensate
(MIT group, PRL 92, 120403 (04))
(JILA, after Nature 424, 47 (03))
(Innsbruck, after Science 305, 1128 (04))
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First evidence of superfluidity of fermion pairing
a
B
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Optical lattice
3D lattice
1D lattice
Entanglement control
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Mott-Insulator transition
Bose-Hubbard model
n3
superfluid
n2
n1
(after Nature 415, 39 (02))
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Fermions in optical lattice
Fermi Hubbard model
Superfluidity of fermion pairing in lattice is
also realized.
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Transport in 1D waveguide
wave guide
Interference ?
Finite temperature semiconductor technique
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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.)
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Condensate (superfluid)
Tc700 nK
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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.)
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Condensate (superfluid)
Tc700 nK
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Interdisciplinary field
Traditional AMO
Precise measurement
Cosmology
Ultracold atoms
Quantum Information
Nonlinear Physics
Soft-matter/ chemistry
Condensed matter