Atom–molecule coherence in a Bose–Einstein condensate

Donley, Elizabeth A.; Claussen, N. R.; Thompson, Sarah T.; Wieman, Carl

doi:10.1038/417529a

Cited by 652 publications

(887 citation statements)

References 26 publications

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“…The goal here is to model a resonantly interacting atomic Bose gas of the type realized in recent experiments 4 . A resonant interaction is the key feature special to a select class of atomic (fermionic 6,7 and bosonic 4 ) systems.…”

Section: Two-channel Feshbach Resonant Modelmentioning

confidence: 99%

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Superfluidity and phase transitions in a resonant Bose gas

2008

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The atomic Bose gas is studied across a Feshbach resonance, mapping out its phase diagram, and computing its thermodynamics and excitation spectra. It is shown that such a degenerate gas admits two distinct atomic and molecular superfluid phases, with the latter distinguished by the absence of atomic off-diagonal long-range order, gapped atomic excitations, and deconfined atomic π-vortices. The properties of the molecular superfluid are explored, and it is shown that across a Feshbach resonance it undergoes a quantum Ising transition to the atomic superfluid, where both atoms and molecules are condensed. In addition to its distinct thermodynamic signatures and deconfined half-vortices, in a trap a molecular superfluid should be identifiable by the absence of an atomic condensate peak and the presence of a molecular one.

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Section: Two-channel Feshbach Resonant Modelmentioning

confidence: 99%

“…2. One may hope that when long-lived molecular condensates are produced, nontrivial behavior of E (1) gap (ν) and the full excitation spectra may be observed in Ramsey fringes 4 , and in Bragg and RF spectroscopy experiments 52,53,54,55 .…”

Section: Msf-asf Phase Transitionmentioning

confidence: 99%

Superfluidity and phase transitions in a resonant Bose gas

2008

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“…This will open new areas for investigation, much as frequency conversion provided for in quantum and nonlinear optics. We note here that photoassociation is not the only possible method which can be used to form coupled atomic and molecular condensates, with Feshbach resonance techniques having been successfully used [21][22][23][24], although this technique would not normally be expected to produce the population oscillations predicted for photoassociation superchemistry.…”

Section: Introductionmentioning

confidence: 99%

Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates

2004

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By stochastic modeling of the process of Raman photoassociation of Bose-Einstein condensates, we show that, the farther the initial quantum state is from a coherent state, the farther the one-dimensional predictions are from those of the commonly used zero-dimensional approach. We compare the dynamics of condensates, initially in different quantum states, finding that, even when the quantum prediction for an initial coherent state is relatively close to the Gross-Pitaevskii prediction, an initial Fock state gives qualitatively different predictions. We also show that this difference is not present in a single-mode type of model, but that the quantum statistics assume a more important role as the dimensionality of the model is increased. This contrasting behavior in different dimensions, well known with critical phenomena in statistical mechanics, makes itself plainly visible here in a mesoscopic system and is a strong demonstration of the need to consider physically realistic models of interacting condensates.

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“…The coherent transformation of a cold atomic gas to molecules in the vicinity of a photo-association [1] or Feshbach [2] resonance has enabled a fascinating probe of quantum dynamical behavior in coupled atom-molecular systems, together with remarkably precise measurements of quantum binding energies. Recent Bosonic experiments have extended the available species to 133 Cs, 87 Rb, and 23 Na [3].…”

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confidence: 99%

Coherent molecular bound states of bosons and fermions near a Feshbach resonance

Drummond

Kheruntsyan

2004

Phys. Rev. A

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We analyze molecular bound states of atomic quantum gases near a Feshbach resonance. A simple, renormalizable field theoretic model is shown to have exact solutions in the two-body sector, whose binding energy agrees well with observed experimental results in both Bosonic and Fermionic cases. These solutions, which interpolate between BEC and BCS theories, also provide a more general variational ansatz for resonant superfluidity and related problems. Since these are many-body systems, it is useful to try to develop the simplest possible field-theoretic model that can explain their behavior. An essential feature of any correct many-body treatment is that the basic theory must be able to reproduce the physics of the two-body interactions. In this paper, we combine previous analytic solutions of a coherently coupled field theory [7-9] with an exact renormalization of the coupling constants [10], in order to obtain analytic predictions for the two-body bound states. This gives a unified picture of any Feshbach resonance experiment and related studies [7][8][9][10][11][12][13][14][15][16][17][18][19][20], provided a small number of observable parameters are available. The predictions will be compared with experimental data and with coupled-channel calculations.To quantitatively model these experiments, consider an effective Hamiltonian for the molecular field ͑⌿ 0 ͒ in the closed channel and the atomic fields ͑⌿ 1͑2͒ ͒ in the free-atom dissociation limit of the open channel:with the commutation (ϩ) or anticommutation (Ϫ) relation ͓⌿ i ͑x , t͒ , ⌿ j † ͑xЈ , t͔͒ ± = ␦ ij ␦͑x − xЈ͒ for Bosonic or Fermionic field operators ⌿ i , respectively. The free Hamiltonian Ĥ 0 includes the usual kinetic energy terms and the potential energies (including internal energies) due to the trap potential បV i ͑x͒, while U ij is the atom-atom, atom-molecule, and molecule-molecule coupling due to s-wave scattering. The atomic and molecular masses are m 1,2 and m 0 = m 1 + m 2 , andgives the bare energy detuning of the molecular state with respect to free atoms. Next, we consider a coherent process of Raman photoassociation or a magnetic Feshbach resonance coupling, giving rise to an overall effective Hamiltonian term in the homo-nuclear case (only with Bosons) [7,8],or, for the case of heteronuclear dimer formation involving either fermions or bosons [9],Here, is the bare atom-molecule coupling responsible for the conversion of free atom pairs into molecules and vice versa. The heteronuclear case can be applied to Fermionic atom pairs in different spin states (⌿ 1 , ⌿ 2 ) combining into a Bosonic molecule ͑⌿ 0 ͒, or pairs of Bosonic and Fermionic atoms combining into a Fermionic molecule, or else to a fully Bosonic case where the atom pairs are not identical. Bosonic homonuclear case. First we consider the fully Bosonic uniform case of Eq. (2), i.e., a single-species atomic BEC (with m 1 ϵ m) coupled to a molecular BEC, where the atomic background energy is chosen to be zero. We ignore inelastic collisions-which is a reasonable approximati...

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Atom–molecule coherence in a Bose–Einstein condensate

Cited by 652 publications

References 26 publications

Superfluidity and phase transitions in a resonant Bose gas

Superfluidity and phase transitions in a resonant Bose gas

Fock-state dynamics in Raman photoassociation of Bose-Einstein condensates

Coherent molecular bound states of bosons and fermions near a Feshbach resonance

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