Effective microscopic models for sympathetic cooling of atomic gases

Onofrio, Roberto; Sundaram, Bala

doi:10.1103/physreva.92.033422

Cited by 8 publications

(30 citation statements)

References 44 publications

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“…(Q m , P m ), respectively, where N b is the number of the coolant atoms (constituting the 'bath') and N p the number of particles of the cooled species. The interaction potential is the one we introduced earlier [15] and is characterized by a range λ, and a strength γ E . Larger interaction strengths γ E obviously increase the thermalization speed.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Our earlier work [15] introduced an effective microscopic model to discuss thermalization dynamics between two atomic species in the nondegenerate regime. A key ingredient was an interaction term intended to extend Caldeira-Leggett models [16][17][18][19][20][21][22][23] to traps confining a finite number of atoms and arbitrary inter-species interaction strength.…”

Section: Introductionmentioning

confidence: 99%

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Simulating sympathetic cooling of atomic mixtures in nonlinear traps

2017

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We discuss the dynamics of sympathetic cooling of atomic mixtures in realistic, nonlinear trapping potentials using a microscopic effective model developed earlier for harmonic traps. We contrast the effectiveness of different atomic traps, such as Ioffe-Pritchard magnetic traps and optical dipole traps, and the role their intrinsic nonlinearity plays in speeding up or slowing down thermalization between the two atomic species. This discussion includes cases of configurations with lower effective dimensionality. From a more theoretical standpoint, our results provide the first exploration of a generalized Caldeira-Leggett model with nonlinearities both in the trapping potential as well as in the interspecies interactions, and no limitations on their coupling strength.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Simulating sympathetic cooling of atomic mixtures in nonlinear traps

2017

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“…In a future study, we will investigate the role of temperature, of the confining potential, and of the accelerated motion of the two clouds [35] that should provide a more accurate model for the damping rate versus velocity and more insights on the nature of the excitations. In particular the ab initio calculation of the damping rate will require to clarify the dissipation mechanism at play in a trapped system where the bandwidth of the excitation spectrum is narrow, in contrast to a genuine CaldeiraLeggett model [39].…”

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confidence: 99%

Critical Velocity and Dissipation of an Ultracold Bose-Fermi Counterflow

et al. 2015

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We study the dynamics of counterflowing bosonic and fermionic lithium atoms. First, by tuning the interaction strength we measure the critical velocity vc of the system in the BEC-BCS crossover in the low temperature regime and we compare it to the recent prediction of Castin et al., Comptes Rendus Physique, 16, 241 (2015). Second, raising the temperature of the mixture slightly above the superfluid transitions reveals an unexpected phase-locking of the oscillations of the clouds induced by dissipation.PACS numbers: 03.75. Kk, 03.75.Ss, 37.10.Gh Superconductivity and superfluidity are spectacular macroscopic manifestations of quantum physics at low temperature. Besides liquid helium 4 and helium 3, dilute quantum gases have emerged over the years as a versatile tool to probe superfluid properties in diverse and controlled situations. Frictionless flows have been observed with both bosonic and fermionic atomic species, in different geometries and in a large range of interaction parameters from the weakly interacting Bose gas to strongly correlated fermionic systems [1][2][3][4][5][6]. Several other hallmarks of superfluidity such as quantized vortices or second sound were also observed in cold atoms [7][8][9].A peculiar feature of superfluid flows is the existence of a critical velocity above which dissipation arises. In Landau's original argument, this velocity is associated with the threshold for creation of elementary excitations in the superfluid: for a linear dispersion relation, it predicts that the critical velocity is simply given by the sound velocity in the quantum liquid. This critical velocity has been measured both in superfluid helium [10] and ultracold atoms [1,[4][5][6]11]. However the recent production of a Bose-Fermi double superfluid [12] raised new questions on Bose-Fermi mixtures [13][14][15][16] and interrogations on the validity of Landau's argument in the case of superfluid counterflow [17][18][19][20][21][22].In this letter, we study the dynamics of a Bose-Fermi superfluid counterflow in the BEC-BCS crossover and at finite temperature. We show how friction arises when the relative velocity of the Bose and Fermi clouds increases and we confirm that damping occurs only above a certain critical relative velocity v c . We compare our measurements to Landau's prediction and its recent generalization v c = c Our Bose and Fermi double-superfluid set-up was previously described in [12]. We prepare vapors of bosonic (B) 7 Li atoms spin-polarized in the second-to-lowest energy state and fermionic (F) 6 Li atoms prepared in a balanced mixture of the two lowest spin states noted |↑ , |↓ . The two species are kept in the same cigar-shaped hybrid magnetic-optical trap in which evaporative cooling is performed in the vicinity of the 832 G 6 Li Feshbach resonance [26]. The final number of fermions N F = 2.5 × 10 5 greatly exceeds that of the bosons N B ∼ 2.5 × 10 4 and the temperature of the sample is adjusted by stopping the evaporation at different trap depths. The thermal pedestal surroundin...

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“…Below the critical inverse temperature, both particles are free to explore the entire trap while, at lower temperatures, each particle is confined on one side of the trap. This can be thought of in terms of a phase separation which diminishes the interaction energy contribution, and the overall scaling with the number of particles, in analogy to the discussion appeared in Sect.III of [6] in terms of stability analysis. At the critical inverse temperature and for an unbalanced mixture, the total interaction energy is given by…”

Section: Analytical Considerationsmentioning

confidence: 99%

“…In previous work [6,7], we explored thermalization in the context of a model where the interaction, both in range and strength, appeared as a generalization of this more familiar Caldeira-Leggett model. Though the earlier context was the sympathetic cooling of atomic gas mixtures, our model was also intended to explore the realm of nonlinearities arising in either, or both, interaction and confining potentials [8].…”

Section: Introductionmentioning

confidence: 99%

Scaling laws for harmonically trapped two-species mixtures at thermal equilibrium

2019

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We discuss the scaling of the interaction energy with particle numbers for a harmonically trapped two-species mixture at thermal equilibrium experiencing interactions of arbitrary strength and range. In the limit of long-range interactions and weak coupling, we recover known results for the integrable Caldeira-Leggett model in the classical limit. In the case of short-range interactions and for a balanced mixture, numerical simulations show scaling laws with exponents that depend on the interaction strength, its attractive or repulsive nature, and the dimensionality of the system. Simple analytic considerations based on equilibrium statistical mechanics and small interspecies coupling quantitatively recover the numerical results. The dependence of the scaling on interaction strength helps to identify a threshold between two distinct regimes. Our thermalization model covers both local and extended interactions allowing for interpolation between different systems such as fully ionized gases and neutral atoms, as well as parameters describing integrable and chaotic dynamics.

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Effective microscopic models for sympathetic cooling of atomic gases

Cited by 8 publications

References 44 publications

Simulating sympathetic cooling of atomic mixtures in nonlinear traps

Simulating sympathetic cooling of atomic mixtures in nonlinear traps

Critical Velocity and Dissipation of an Ultracold Bose-Fermi Counterflow

Scaling laws for harmonically trapped two-species mixtures at thermal equilibrium

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