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Spectroscopy of Superfluid Atomic Fermi Gases

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. Contents.

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Spectroscopy of Superfluid Atomic Fermi Gases

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  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.

  3. Science and Physics World ranked the observation of Fermi condensates among the top ten scientific breakthroughs of the year 2004 Fermion pairs near the Feshbach Resonance 2004 Jin, Ketterle BEC of molecules (dimers of two Fermions) 2003-2004 Grimm, Jin, Ketterle, Salomon Density profile throughout the crossover Grimm 2004 Heat capasity Thomas 2005 Collective modes Thomas 2004, Grimm 2004 Vortices Ketterle 2005 Pairing gap Grimm 2004

  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

  5. Driving a transition between a paired and an unpaired state Spectroscopy of the pairing gap D | 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, 230404 (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)

  6. Analogy to metallic superconductors D normal metal superconductor | 3 > eV | 2 > | 1 > In the following: 1,2,3 = g’,g,e

  7. Superfluid with a pseudogap Feshbach detuning Picture from Stajic et al. 2004

  8. Equilibrium state: Resonance superfluidity with a pseudogap M. Holland, S.J.J.M.F. Kokkelmans, M.L. Chiofalo, R. Walser, PRL 87, 120406 (2001) c.f. E. Timmermans, K. Furuya, P.W. Milonni, A.K. Kerman, Phys.Lett.A 63, 130402 (2002) Y. Ohashi and A. Griffin, PRL 89, 130402 (2002) J. Stajic, J.N. Milstein, Q. Chen, M.L. Chiofalo, M.J. Holland, K. Levin, PRA 69, 063610 (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, 220404 (2004)

  9. Spectrum

  10. The spectrum is calculated using second-order perturbation theory and the local density approximation using Thomas-Fermi density distribution

  11. The calculated spectra at different temperatures Critical temperature Tc ~ 0.27 TF J. Kinnunen, M. Rodríguez and P. Törmä, Science 305, 1131 (2004)

  12. 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

  13. D(z=0) RF peak position Lowest Andreev state T = 0 J. Martikainen and P. Törmä, cond-mat/0505275

  14. 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

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