Two-species magneto-optical trap with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>40</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">K</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>87</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Rb</mml:mi></mml:math>

Goldwin, J.; Papp, Scott B.; DeMarco, Brian; Jin, D. S.

doi:10.1103/physreva.65.021402

Cited by 81 publications

(76 citation statements)

References 17 publications

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“…The lowest temperatures achieved to date in this system are around 0.2 T F -limited by Pauli blocking as well as a number of technical considerations [3]. In other experiments, the rethermalization of fermion atoms by elastic collisions with a bath of ultracold bosons is exploited; realized by mixtures of 6 Li and 7 Li at Rice [4], and at ENS [5], and more recently by mixtures of 40 K atoms and 87 Rb atoms at JILA [6].…”

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confidence: 99%

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Signatures of Resonance Superfluidity in a Quantum Fermi Gas

et al. 2002

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In this letter, we predict a direct and observable signature of the superfluid phase in a quantum Fermi gas, in a temperature regime already accessible in current experiments. We apply the theory of resonance superfluidity to a gas confined in a harmonic potential and demonstrate that a significant increase in density will be observed in the vicinity of the trap center.PACS numbers: 03.75. Fi, Following the successful realization of Bose-Einstein condensation (BEC) in confined vapors [1], it is natural to consider possibilities for observing the analogous superfluid phase transition in a dilute Fermi gas. Quantum degeneracy has already been demonstrated in a twocomponent In order to observe a superfluid phase transition at critical temperatures as high as 0.2 T F , the existence of a strong coupling mechanism which could lead to a significant amount of Cooper pairing is necessary. Several theoretical papers have presented models to investigate this regime, essentially based on application of the Bardeen-Cooper-Schrieffer (BCS) [7] theory of superconductivity. These approaches consider dilute Fermi vapors in which the two body scattering processes are characterized by a large negative scattering length a [8]. Under such conditions the relevant length scale-the spatial extent of the Cooper pair-may become comparable to the average interparticle spacing. This places the system in a crossover region from the BCS superfluidity of momentum-correlated fermion pairs to the BEC of tightly bound composite bosons. In this crossover regime, fluctuations play a crucial role [9] and must be addressed.Eventually, as the coupling is increased, it becomes necessary to construct a theory in which explicit treatment of the composite bosonic states is made. Such an approach was proposed in the context of hightemperature superconductivity [10] and is based on an effective many-body Hamiltonian, in which quasibound pairs are explicitly treated as resonance states embedded in the continuum of the Fermi sea. Such resonances are ubiquitous in atomic physics, where, for example, a Feshbach resonance [11] can be utilized to tune a quasibound state through threshold, providing an explicit microscopic basis for a theory of resonance superfluidity [12,13].A convincing method for detecting the superfluidity will be required. Various approaches have been proposed; including measurements of the pair distribution [14], experiments involving the breakup of the Cooper pairs [15], measurements of the moment of inertia [16], and probes of collective excitations [17,18]. In this letter, we show that a more straightforward and direct experimental signature of the transition to the superfluid phase is provided by the density characteristics in an inhomogeneous system. We demonstrate that in a harmonic trap, the superfluid state is manifest as the appearance of a bulge in the central atomic density. To this aim we derive a theory of resonance superfluidity including the description of external confinement. FIG. 1. Real (solid line) and imaginary (dashed...

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“…Direct measures of this behavior are possible by the study of the propagation of sound waves. We have applied our method here to 40 K, but a similar approach is easy to derive for other interesting atoms, including in particular 6 Li which is the other fermionic alkali currently being investigated experimentally. .…”

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Signatures of Resonance Superfluidity in a Quantum Fermi Gas

et al. 2002

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“…(36) and Eq. (13). However, instead of |F , here the expectation value is calculated with respect to the BCS ground state, |Φ 0 .…”

Section: Mixture Of Bec and Superfluid Fermi Gasmentioning

confidence: 99%

“…As a result, the recent experiments that achieved quantum degeneracy in 6 Li have used 7 Li, a boson, to sympathetically cool the 6 Li atoms [9]. This procedure is also being applied to cool 40 K using 87 Rb [13]. Therefore, it appears likely that future experiments on degenerate Fermi gases will be associated with a Bose gas with a non-negligible boson-fermion two-body interaction.…”

Section: Introductionmentioning

confidence: 99%

Quasiparticle spectrum and dynamical stability of an atomic Bose-Einstein condensate coupled to a degenerate Fermi gas

Zhang

et al. 2002

Phys. Rev. A

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The quasiparticle excitations and dynamical stability of an atomic Bose-Einstein condensate coupled to a quantum degenerate Fermi gas of atoms at zero temperature is studied. The Fermi gas is assumed to be either in the normal state or to have undergone a phase transition to a superfluid state by forming Cooper pairs. The quasiparticle excitations of the Bose-Einstein condensate exhibit a dynamical instability due to a resonant exchange of energy and momentum with quasiparticle excitations of the Fermi gas. The stability regime for the bosons depends on whether the Fermi gas is in the normal state or in the superfluid state. We show that the energy gap in the quasiparticle spectrum for the superfluid state stabilizes the low energy energy excitations of the condensate. In the stable regime, we calculate the boson quasiparticle spectrum, which is modified by the fluctuations in the density of the Fermi gas.

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“…The collisionality of such gases has been increased by mixing them either with a fermion gas in a different spin state [2][3][4][5][6] or with a Bose-Einstein condensed gas of bosonic atoms in numbers exceeding those of the fermions by a few orders of magnitude [7][8][9][10][11]. However, the collision rate of a fermion-fermion mixture at low temperatures is limited by the Pauli blocking of collisions as a result of the occupation of final states around the Fermi level and, in the case of a boson-fermion mixture, the collisionality can be strongly diminished by superfluidity of the condensate [12].…”

Section: Introductionmentioning

confidence: 99%

Effects of collisions against thermal impurities in the dynamics of a trapped fermion gas

et al. 2004

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We present a theoretical study of the dynamical behavior of a gas made of ultracold fermionic atoms, which during their motions can collide with a much smaller number of thermal bosonic impurities. The atoms are confined inside harmonic traps and the interactions between the two species are treated as due to s-wave scattering with a negative scattering length modeling the 40 K-87 Rb fermion-boson system. We set the fermions into motion by giving a small shift to their trap center and examine two alternative types of initial conditions, referring to (i) a close-to-equilibrium situation in which the two species are at the same temperature (well below the Fermi temperature and well above the Bose-Einstein condensation temperature); and (ii) a far-from-equilibrium case in which the impurities are given a Boltzmann distribution of momenta while the fermions are at very low temperatures. The dynamics of the gas is evaluated by the numerical solution of the Vlasov-Landau equations for the one-body distribution functions, supported by some analytical results on the collisional properties of a fermion gas. We find that the trapped gaseous mixture is close to the collisionless regime for values of the parameters corresponding to current experiments, but can be driven towards a collisional regime even without increasing the strength of the interactions, either by going over to heavier impurity masses or by matching the width of the momentum distribution of the impurities to the Fermi momentum of the fermion gas.

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Two-species magneto-optical trap with40Kand87Rb

Cited by 81 publications

References 17 publications

Signatures of Resonance Superfluidity in a Quantum Fermi Gas

Signatures of Resonance Superfluidity in a Quantum Fermi Gas

Quasiparticle spectrum and dynamical stability of an atomic Bose-Einstein condensate coupled to a degenerate Fermi gas

Effects of collisions against thermal impurities in the dynamics of a trapped fermion gas

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