1. Spectroscopy of Superfluid Atomic Fermi Gases
Päivi Törmä
University of Jyväskylä
Jami Kinnunen
Mirta Rodriguez
Timo Koponen
Jani Martikainen
International Conference on Finite Fermionic Systems
Nilsson Model 50 Years

2. Contents
RF-spectroscopy of the pairing gap; theory related to the experiments of R. Grimm‘s group
J. Kinnunen, M. Rodriguez, P.T.
Spectroscopy and density response in an optical lattice
T. Koponen, J. Martikainen, J. Kinnunen, P.T.
Quasi 2D superfluid Fermi gases
J. Martikainen, P.T.
Spectra beyond linear response
J. Kinnunen, P.T.
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3. BEC of molecules (dimers of two Fermions) 2003-2004
Science and Physics World ranked the observation of Fermi condensates among the top ten scientific breakthroughs of the year 2004
BEC of molecules (dimers of two
Fermions)
Grimm, Jin, Ketterle, Salomon
Fermion pairs near the Feshbach
Resonance 2004
Jin, Ketterle
Density profile throughout the
crossover
Grimm 2004
Heat capasity
Thomas 2005
Collective modes
Thomas 2004,
Grimm 2004
Vortices
Ketterle 2005
Pairing gap Grimm 2004
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4. The pairing gap in strongly interacting Fermi gases
J. Kinnunen, M. Rodriguez, and P. Törmä,
Science 305, 1131, 2004
C. Chin, M. Bartenstein, A. Altmayer,
S. Riedl, S. Jochim, J.H. Denschlag,
and R. Grimm, Science 305, 1128, 2004
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5. Spectroscopy of the pairing gapD
Driving a transition between a paired and an unpaired state
| 3 >
| 2 >
| 1 >
Probing the superfluid excitation gap
- P. Törmä and P. Zoller, PRL 85, 487 (2000)
RF-spectroscopy of mean field effects
- C. Regal and D. Jin, PRL 90, (2003)
- S. Gupta, Z. Hadzibabic, M.W. Zwierlein, C.A. Stan,
K. Dieckmann, C.H. Schunck, E.G.M. van Kempen,
B.J. Verhaar, W. Ketterle, Science 300, 1723 (2003)
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6. Analogy to metallic superconductors
| 3 >
superconductor
normal metal eV
| 2 >
| 1 >
In the following: 1,2,3 = g’,g,e
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7. Superfluid with a pseudogap
Feshbach detuning
Picture from Stajic et al. 2004
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8. Equilibrium state: Resonance superfluidity with a pseudogap
M. Holland, S.J.J.M.F. Kokkelmans, M.L. Chiofalo, R. Walser, PRL 87, (2001)
c.f. E. Timmermans, K. Furuya, P.W. Milonni, A.K. Kerman, Phys.Lett.A 63, (2002)
Y. Ohashi and A. Griffin, PRL 89, (2002)
Mention Eagles, Leggett, Nozieres and Schmitt-Rink
J. Stajic, J.N. Milstein, Q. Chen, M.L. Chiofalo, M.J. Holland, K. Levin, PRA 69, (2004)
Q.J. Chen, I. Kosztin, B. Janko, and K. Levin, PRL 81, 4708 (1998)
c.f. A. Perali, P. Pieri, L. Pisani, G.C. Strinati, PRL 92, (2004)
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9. Spectrum
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10. The spectrum is calculated using second-order perturbation theory
and the local density approximation using Thomas-Fermi
density distribution
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11. Critical temperature Tc ~ 0.27 TF
The calculated spectra at different temperatures
Critical temperature Tc ~ 0.27 TF
J. Kinnunen, M. Rodríguez and P. Törmä, Science 305, 1131 (2004)
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15. Quasi 2D Superfluid Fermi gases
Effectively 2D system (e.g. optical lattices)
Steps in order parameter when consequtive trap levels become populated
C.f. finite size effects recently observed in thin films Guo et al., Science 306, 1915 (2004)
C.f. 3He on 4He film: Steps in magnetization, Physics Today, June 1998, p. 30
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19. D(z=0) RF peak position Lowest Andreev state T = 0
J. Martikainen and P. Törmä, cond-mat/
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20. Conclusions
Spectra from resonance superfluidity theory and linear response confirm that the pairing gap of a Fermi condensate was observed
Quasi 2D Fermions: steps in order parameter
Have to take into account for all non-trivial states and different responses (e.g. spin)
Important e.g. for quantitative comparison of different cross-over models
Comes up because complicated many-body state + high coherence
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