Dynamical formation of the unitary Bose gas

Colussi, V. E.; Musolino, S.; Kokkelmans, Sjjmf Servaas

doi:10.1103/physreva.98.051601

Cited by 15 publications

(64 citation statements)

References 59 publications

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“…We model a uniform gas of identical spinless bosons interacting via pairwise interactions described by the single-channel many-body Hamiltonian [10][11][12][13]30]. To fix the free parameters of the separable potential, we first set the strength of the potential, g = U 0 Γ, where U 0 = 4π 2 a/m and Γ = (1 − 2aΛ/π) −1 , to reproduce the exact two-body T matrix in the zero-energy limit [20,31]. To fix Λ, we follow Ref.…”

Section: A Many-body Equationsmentioning

confidence: 99%

“…To fix Λ, we follow Ref. [20] and set Λ = 2/πā to obtain finite-range corrections to the binding energy of the Feshbach molecule E b − 2 /m(a −ā) 2 , valid only to first order in 1/Λa, and whereā = 0.955r vdW is the mean scattering length that depends on the van der Waals length r vdW , for a particular atomic species [1]. Consequently, at unitarity we obtain a finite interaction strength g = −π 3 2ā /m for a → ∞.…”

Section: A Many-body Equationsmentioning

confidence: 99%

“…[11]. Understanding the role of the Efimov effect [17,18] and dynamics of higher-order correlations [19][20][21] in the quenched unitary Bose gas remains, however, an ongoing pursuit in the community.…”

Section: Introductionmentioning

confidence: 99%

“…Here, the size of a molecule is much smaller than the mean interparticle separation, and the distinction between unbound and bound atoms is physically meaningful again [22]. In the unitary regime, unbound pairs progressively localize onto the scale of the interparticle spacing, purely due to manybody effects [20]. The nature of these embedded dimers is reflected by a universal time-dependent size a eff , fit to the universal form k n a eff = 1.58 + 3.44…”

Section: Introductionmentioning

confidence: 99%

“…II B) for Bose gases, and develop the theory of bound pairs in the unitary regime discussed in Ref. [20] (Sec. II C).…”

Section: Introductionmentioning

confidence: 99%

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Pair formation in quenched unitary Bose gases

2019

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We study a degenerate Bose gas quenched to unitarity by solving a many-body model including three-body losses and correlations up to second order. As the gas evolves in this strongly interacting regime, the buildup of correlations leads to the formation of extended pairs bound purely by manybody effects, analogous to the phenomenon of Cooper pairing in the BCS regime of the Fermi gas. Through fast sweeps away from unitarity, we detail how the correlation growth and formation of bound pairs emerge in the fraction of unbound atoms remaining after the sweep, finding quantitative agreement with experiment. We comment on the possible role of higher-order effects in explaining the deviation of our theoretical results from experiment for slower sweeps and longer times spent in the unitary regime. though these findings, combined with studies of loss dy-52 namics in Refs. [10-12], are consistent with the univer-53 sality hypothesis, a macroscopic population of Efimov 54 trimers was observed in Ref. [11]. Understanding the 55 role of the Efimov effect [17, 18] and dynamics of higher-56 order correlations [19-21] in the quenched unitary Bose 57 gas remains however an ongoing pursuit in the commu-58 nity. 59 60The difficulties of probing the system at unitarity re-61 quire that experiments return to the more stable and 62 better-understood weakly-interacting regime. During the 63 course of the experiment, we have to distinguish differ-64 ent types of atomic pairs: (i) pairs of atoms with op-65 posite momentum, analogous to Cooper pairs in Fermi 66 gases, (ii) embedded dimers at unitarity whose size is de-67 termined by the mean interparticle separation, and (iii) 68 specific ramp, we find a molecular fraction ∼ 10%, which 472 is compatible with the experimental estimate in Ref. [12]. 473 By comparing three values A = {0.28, 0.20, 0.18} to the 474 0.3 µs/G experimental data we find that A = 0.20 pro-475 vides the best fit of the experimental results over the full 476 range of t hold considered in this work. For the slower 6 477 µs/G ramp, we find that A = 0.20 gives good agreement 478 at early-times until roughly t hold 0.5t n . We discuss 479 possible sources of this discrepancy at longer t hold at the 480 conclusion of this section. 481 Our results for N free over a range of 1/R are com-482 pared against the experimental findings in Ref. [12] as 483 shown in Fig. 5. The results shown in Fig. 5 are at 484 fixed t hold = 1.9t n , nearing the limit of validity of our 485 model [see Sec. II A]. The intuitive picture, discussed 486 in Secs. II B, II C and illustrated in Fig. 2 provides a 487 way to understand our results particularly at this later 488 time where the bound pairs at unitarity play a dom-489 inant role [see Fig. 3]. For smaller ramp rates, the 490 largest values of N free shown in Fig. 5 result from the 491 fast-sweep projection occurring further away from unitar-492 ity where the overlap between embedded dimers (φ D (k)) 493 with molecules (φ * (k)) becomes minimal. We find good 494 agreement with experiment only ...

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Section: A Many-body Equationsmentioning

confidence: 99%

Section: A Many-body Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…II B) for Bose gases, and develop the theory of bound pairs in the unitary regime discussed in Ref. [20] (Sec. II C).…”

Section: Introductionmentioning

confidence: 99%

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Pair formation in quenched unitary Bose gases

2019

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Universal dynamic scaling and Contact dynamics in quenched quantum gases

Cui,

Zhou,

Sun

2023

Front. Phys.

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Scattering hypervolume for ultracold bosons from weak to strong interactions

et al. 2019

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Dynamical formation of the unitary Bose gas

Cited by 15 publications

References 59 publications

Pair formation in quenched unitary Bose gases

Pair formation in quenched unitary Bose gases

Universal dynamic scaling and Contact dynamics in quenched quantum gases

Scattering hypervolume for ultracold bosons from weak to strong interactions

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