Spin-Singlet Bose-Einstein Condensation of Two-Electron Atoms

Takasu, Yoshio; Maki, Kazumi; Komori, K.; Takano, T.; Honda, K.; Kumakura, M.; Yabuzaki, T.; Takahashi, Yoshiro

doi:10.1103/physrevlett.91.040404

Cited by 364 publications

(297 citation statements)

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“…It has seven stable isotopes (five zero-spin bosons and two fermions), and a closed-shell, singlet-spin electronic structure. Both bosonic [25][26][27][28] and fermionic [29,30] The existence of magnetically tunable Feshbach resonances requires coupling between a continuum scattering state of the atomic pair and a molecular state that crosses it as a function of magnetic field. For pairs of alkali-metal atoms, this coupling is provided by the difference between the singlet and triplet potential curves and by the magnetic dipolar interaction between the electron spins.…”

Section: Introductionmentioning

confidence: 99%

Prospects of forming ultracold molecules in2Σstates by magnetoassociation of alkali-metal atoms with Yb

2013

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Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We explore the feasibility of producing ultracold diatomic molecules with nonzero electric and magnetic dipole moments by magnetically associating two atoms, one with zero electron spin and one with nonzero spin. Feshbach resonances arise through the dependence of the hyperfine coupling on internuclear distance. We survey the Feshbach resonances in diatomic systems combining the nine stable alkali-metal isotopes with those of Yb, focusing on the illustrative examples of RbYb and CsYb. We show that the resonance widths may expressed as a product of physically comprehensible terms in the framework of Fermi's golden rule. The resonance widths depend strongly on the background scattering length, which may be adjusted by selecting the Yb isotope, and on the hyperfine coupling constant and the magnetic field. In favorable cases the resonances may be over 100 mG wide.

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Section: Introductionmentioning

confidence: 99%

Prospects of forming ultracold molecules in2Σstates by magnetoassociation of alkali-metal atoms with Yb

2013

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“…A small loss rate coefficient leads to longer observation times. Although we have used calcium as an example system, we expect our conclusions to remain valid for other alkalineearth atoms as well as atoms with similar electronic structure like ytterbium [21]. Optical Feshbach resonances seem to be a promising tool that will allow a tunable interaction strength in atomic systems which do not have magnetic Feshbach resonances.…”

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“…Optical Feshbach control can be also applied to other atomic systems having a similar electronic structure. The recent Bose-Einstein condensation of ytterbium [21] makes this system especially interesting.The theoretical description of optical Feshbach resonances and the closely related photoassociation (PA) process is well established [14,15,16]. The elastic and inelastic scattering rates due to a single photoassociation resonance level depends on (1) the natural line width Γ e,nat ≈ 2Γ A of the excited molecular level e, (2) the stimulated width Γ eg (ε r ) that couples the excited level to the s-wave collision of the ground state g at relative kinetic energy ε r , and (3) the detuning ∆ − ∆ e from optical resonance.…”

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Optical tuning of the scattering length of cold alkaline-earth-metal atoms

2005

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It is possible to tune the scattering length for the collision of ultra-cold 1 S0 ground state alkaline-earth atoms using an optical Feshbach resonance. This is achieved with a laser far detuned from an excited molecular level near the frequency of the atomic intercombination 1 S0-3 P1 transition. Simple resonant scattering theory, illustrated by the example of 40 Ca, allows an estimate of the magnitude of the effect. Unlike alkali metal species, large changes of the scattering length are possible while atom loss remains small, because of the very narrow line width of the molecular photoassociation transition. This raises prospects for control of atomic interactions for a system without magnetically tunable Feshbach resonance levels.PACS numbers: 34.50. Rk, 34.10.+x, 32.80.Pj In recent years the ability to change the interaction between ultra-cold colliding atoms has opened the way for new and exciting experiments with ultra-cold atomic gases. The observation of a Bose-Einstein condensate (BEC) in atomic cesium [1] would have been impossible without the ability to change the interaction from being attractive to being repulsive. More impressively, time-varying interactions have allowed the creation of condensates of two-atom molecules starting from an atomic Bose condensate [2,3]. Most recently, the observation of the condensation of pairs of fermionic [4] atoms has started investigations into the so-called BEC-BCS crossover [5], where BCS is the abbreviation for the BardeenCooper-Schrieffer phase transition in a fermionic gas [6].The key to these developments has been the ability to change the interaction between atoms by a magnetically-tuned Feshbach resonance [7]. Theoretical discussion of the properties of these resonances can be found in Refs. [8,9,10,11]. The interaction between the atoms at ultra-cold temperature can be characterized by a single parameter, the scattering length [12,13], which can be controlled in sign and magnitude using these resonances.Another way to change the scattering length of two colliding atoms is to optically couple the ground scattering state with an excited bound state [14]. These optical Feshbach resonances are theoretically analyzed in Refs. [15,16] and implemented experimentally in Refs. [17,18]. The recent experiment of Theis et al. [18] with 87 Rb atoms showed, however, that a significant change of the scattering length is accompanied with substantial loss of atoms. The same is true if a twocolor Raman process is used [19].In this paper we discuss the optical tuning of scattering lengths in ultra-cold alkaline-earth atom vapors. To do so we will assume that the laser is far detuned from excited molecular states near the intercombination transition, 1 S 0 -3 P 1 , as recently analyzed in Ref. [20]. We show that significant changes of the scattering strength can be achieved without the excessive atom loss that plagues experiments with alkali-metal gases [18]. Prospects for an optically tuned scattering length in ultra-cold alkaline-earth vapors seems to be particularly a...

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“…We have also shown how in a far-fromequilibrium experiment on a fermion gas at T Ӎ 0 the addition of bosonic impurities with momentum spread around the Fermi momentum p F could induce an enhancement of colli- sionality. Due to the dependence of the collision rate on the mass of the impurities, a further increase of collisionality could be achieved by choosing as impurities heavy particles such as 133 Cs [20] and 172 Yb [21] atoms, or strongly bound molecules.…”

Section: Summary and Concluding Remarksmentioning

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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Spin-Singlet Bose-Einstein Condensation of Two-Electron Atoms

Cited by 364 publications

References 22 publications

Prospects of forming ultracold molecules in2Σstates by magnetoassociation of alkali-metal atoms with Yb

Prospects of forming ultracold molecules in2Σstates by magnetoassociation of alkali-metal atoms with Yb

Optical tuning of the scattering length of cold alkaline-earth-metal atoms

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

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