Imbalanced Fermi Gases

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Imbalanced Fermi Gases
Masud Haque Koos Gubbels Mathijs Romans Arnaud
Koetsier Henk Stoof Guthrie Partridge Wenhui
Li Yean-an Liao Randy Hulet
Utrecht University
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Imbalanced Fermi Mixture (I)

• Atomic Fermi mixtures in an optical trap

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Imbalanced Fermi Mixture (II)

• Up to recently only . However, the
  most recent experiments do not have this
  condition any longer. This means that

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MIT Science experiment (I)

• Uses rotation to create vortices and measures
  density profiles after expansion and magnetic
  field sweep

M.W. Zwierlein et al., Science 311, 492 (2006).
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MIT Science experiment (II)
M.W. Zwierlein et al., Science 311, 492 (2006).
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Rice Science experiment (I)

• Uses in-situ imaging

G.B. Partridge et al., Science 311, 503 (2006).
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Rice Science experiment (II)
G.B. Partridge et al., Science 311, 503 (2006).
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Zero Temperature Theory (I)

• Using the BCS ansatz we find for the homogeneous
  case

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Zero Temperature Theory (II)

• Local-density theory and BCS ansatz

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Zero Temperature Theory (III)

• Comparison with Rice experiment

M. Haque and H.T.C. Stoof, PRA 74, 011602(R)
(2006). See also F. Chevy, PRL 96, 130401
(2006) and T.N. De Silva and E.J. Mueller, PRA
73, 051602(R) (2006).
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MIT Nature experiment

• Measures density
• profiles after
• expansion

M.W. Zwierlein et al., Nature 442, 54 (2006).
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Nonzero Temperature Theory (I)

• Proposed (universal) phase diagram

K.B. Gubbels et al., PRL 97, 210402 (2006).
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Nonzero Temperature Theory (II)

• In-situ density profiles are again calculated in
  local-density approximation

K.B. Gubbels et al., PRL 97, 210402 (2006).
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Nonzero Temperature Theory (III)

• Comparison with MIT experiment

K.B. Gubbels et al., PRL 97, 210402 (2006).
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Rice PRL experiment (I)

• Uses in-situ imaging

G.B. Partridge et al., PRL 97, 190407 (2006).
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Rice PRL experiment (II)

• Comparison between theory and experiment

G.B. Partridge et al., PRL 97, 190407 (2006).
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Rice PRL experiment (III)

• Comparison between low and high
  temperature

G.B. Partridge et al., PRL 97, 190407 (2006).
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Rice PRL experiment (IV)

• Superfluid core shape

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Conclusions and Outlook

• Our (universal) phase diagram is able to explain
  the contradictions between the MIT and Rice
  experiments.
• Remaining problem is the absolute temperature
  scale. Requires inclusion of fluctuations into
  the theory. We are working on this!
• Imbalanced Fermi gases in optical lattices and
  neutron stars!

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The Quantum Fluids and Solids Group

• Students Koos Gubbels
• Mathijs Romans
• Arnoud Koetsier
• Postdocs Masud Haque (Dresden)
• Pietro Massignan
• Staff Henk Stoof
• Special thanks
• Randy Hulet