Resonance Superfluidity in a Quantum Degenerate Fermi Gas

Holland, Murray; Kokkelmans, Sjjmf Servaas; Chiofalo, M. L.; Walser, Reinhold

doi:10.1103/physrevlett.87.120406

Cited by 503 publications

(571 citation statements)

References 26 publications

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“…Later work on the equilibrium polariton condensate in models of the basic form (1) includes generalisations to include propagating photons [16,17], decoherence [14], and more realistic approaches to disorder [15,19]. The same theoretical framework has also been applied to condensation in atomic gases of fermions [33,34].…”

Section: Background and Basic Modelmentioning

confidence: 99%

The new physics of non-equilibrium condensates: insights from classical dynamics

Eastham¹

2007

J. Phys.: Condens. Matter

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Abstract. We discuss the dynamics of classical Dicke-type models, aiming to clarify the mechanisms by which coherent states could develop in potentially non-equilibrium systems such as semiconductor microcavities.We present simulations of an undamped model which show spontaneous coherent states with persistent oscillations in the magnitude of the order parameter. These states are generalisations of superradiant ringing to the case of inhomogeneous broadening. They correspond to the persistent gap oscillations proposed in fermionic atomic condensates, and arise from a variety of initial conditions. We show that introducing randomness into the couplings can suppress the oscillations, leading to a limiting dynamics with a time-independent order parameter. This demonstrates that non-equilibrium generalisations of polariton condensates can be created even without dissipation. We explain the dynamical origins of the coherence in terms of instabilities of the normal state, and consider how it can additionally develop through scattering and dissipation.

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Section: Background and Basic Modelmentioning

confidence: 99%

The new physics of non-equilibrium condensates: insights from classical dynamics

Eastham¹

2007

J. Phys.: Condens. Matter

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“…This makes it possible to study the system as it evolves from a dilute Fermi gas with weak attractive interactions to a bosonic gas of diatomic molecules. This transition from a superfluid BCS state to Bose Einstein condensation (BEC) has been the subject of many experimental [2,3,4,5,6,7,8,9,10,11,12] and theoretical works [13,14,15,16,17,18,19,20,21,22,23].…”

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confidence: 99%

Density-functional theory for fermions close to the unitary regime

Bhattacharyya

Papenbrock

2006

Phys. Rev. A

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We consider interacting Fermi systems close to the unitary regime and compute the corrections to the energy density that are due to a large scattering length and a small effective range. Our approach exploits the universality of the density functional and determines the corrections from the analyical results for the harmonically trapped two-body system. The corrections due to the finite scattering length compare well with the result of Monte Carlo simulations. We also apply our results to symmetric neutron matter.PACS numbers: 03.75. Ss,03.75.Hh,05.30.Fk,21.65.+f Ultracold fermionic atom gases have attracted a lot of interest since Fermi degeneracy was achieved by DeMarco and Jin [1]. These systems are in the metastable gas phase, as three-body recombinations are rare. Most interestingly, the effective two-body interaction itself can be controlled via external magnetic fields. This makes it possible to study the system as it evolves from a dilute Fermi gas with weak attractive interactions to a bosonic gas of diatomic molecules. This transition from a superfluid BCS state to Bose Einstein condensation (BEC) has been the subject of many experimental [2,3,4,5,6,7,8,9,10,11,12] and theoretical works [13,14,15,16,17,18,19,20,21,22,23].At the midpoint of this transition, the two-body system has a zero-energy bound state, and the scattering length diverges. If other parameters as the effective range of the interaction can be neglected, the interparticle spacing becomes the only relevant length scale. This defines the unitary limit. In this limit, the energy density is proportional of that of a free Fermi gas, the proportionality constant denoted by ξ. Close to the unitary limit, corrections are due to a finite, large scattering length a and a small effective range r 0 of the potential. Within the local density approximation (LDA), the energy density is given asHere,is the energy density of the free Fermi gas. . We are not aware of any estimate for the constant c 2 in Eq. (1) that concerns the correction due to a small effective range. It is the purpose of this work to fill this gap. This is particularly interesting as experiments also have control over the effective range. Note that the regime of a large effective range has recently been discussed by Schwenk and Pethick [20].In this work, we determine the coefficients c 1 , and c 2 via density functional theory. Recall that the density functional is supposed to be universal, i.e. it can be used to solve the N -fermion system for any particle number N , and for any external potential. Exploiting the universality of the density functional, the parameters c 1 and c 2 can be obtained from a fit to an analytically known solution, i.e. the harmonically trapped two-fermion system [33]. This simple approach has recently been applied [27] to determine the universal constant ξ, and will be followed and extended below.Let us briefly turn to the harmonically trapped twofermion system. The wave function u(r) in the relative coordinate r = r 1 − r 2 of the spin-singlet state is ...

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“…Major current experimental and experimental efforts are directed towards the exploration of the crossover between the Bardeen-Cooper-Schrieffer (BCS) state of fermionic atoms and BEC of bosonic molecules as the system crosses a Feshbach resonance [14]. In the vicinity of these resonances, the system enters a strongly interacting regime that offers a challenge for many-body theories [15,16].…”

Section: Introductionmentioning

confidence: 99%

Boson-fermion coherence in a spherically symmetric harmonic trap

Miyakawa

Meystre

2005

Phys. Rev. A

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We consider the photoassociation of a low-density gas of quantum-degenerate trapped fermionic atoms into bosonic molecules in a spherically symmetric harmonic potential. For a dilute system and the photoassociation coupling energy small compared to the level separation of the trap, only those fermions in the single shell with Fermi energy are coupled to the bosonic molecular field. Introducing a collective pseudo-spin operator formalism we show that this system can then be mapped onto the Tavis-Cummings Hamiltonian of quantum optics, with an additional pairing interaction. By exact diagonalization of the Hamiltonian, we examine the ground state and low excitations of the BoseFermi system, and study the dynamics of the coherent coupling between atoms and molecules. In a semiclassical description of the system, the pairing interaction between fermions is shown to result in a self-trapping transition in the photoassociation, with a sudden suppression of the coherent oscillations between atoms and molecules. We also show that the full quantum dynamics of the system is dominated by quantum fluctuations in the vicinity of the self-trapping solution.

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Resonance Superfluidity in a Quantum Degenerate Fermi Gas

Cited by 503 publications

References 26 publications

The new physics of non-equilibrium condensates: insights from classical dynamics

The new physics of non-equilibrium condensates: insights from classical dynamics

Density-functional theory for fermions close to the unitary regime

Boson-fermion coherence in a spherically symmetric harmonic trap

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