Andreev–Bashkin effect in superfluid cold gases mixtures

Nespolo, Jacopo; Astrakharchik, G. E.; Recati, Alessio

doi:10.1088/1367-2630/aa93a0

Cited by 58 publications

(81 citation statements)

References 48 publications

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“…4. Importantly, one expects that Andreev-Bashkin drag [31] is maximal in the 2SF phase in the vicinity of the transition to PSF [32,33]. In this case, a superflow imposed on one component induces a supercurrent in the second component which is dragged without any energy dissipation.…”

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confidence: 99%

Quantum droplets of bosonic mixtures in a one-dimensional optical lattice

Morera

Astrakharchik

Polls

et al. 2020

Phys. Rev. Research

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We demonstrate the existence of quantum droplets in two-component one-dimensional Bose-Hubbard chains. The droplets exist for any strength of repulsive intra-species interactions provided they are balanced by comparable attractive inter-species interactions. The ground-state phase diagram is presented and the different phases are characterized by examining the density profile and off-diagonal one-and two-body correlation functions. A rich variety of phases is found, including atomic superfluid gases, atomic superfluid droplets, pair superfluid droplets, pair superfluid gases and a Mott-insulator phase. A parameter region prone to be experimentally explored is identified, where the average population per site is lower than three atoms, thus avoiding three-body losses. Finally, the bipartite entanglement of the droplets is found to have a non-trivial dependence on the number of particles.

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confidence: 99%

Quantum droplets of bosonic mixtures in a one-dimensional optical lattice

Morera

Astrakharchik

Polls

et al. 2020

Phys. Rev. Research

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“…A more rigorous approach would be to use an RG treatment which includes density and phase fluctuations on equal footing [64]. The two-component Villain model [65] for bosons of the same mass (which can be extended to bosons of different masses straightforwardly, see (25) in [22]) reads…”

Section: Phonon Excitationsmentioning

confidence: 99%

Coupled superfluidity of binary Bose mixtures in two dimensions

2019

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We consider a two-component Bose gas in two dimensions at low temperature with short-range repulsive interaction. In the coexistence phase where both components are superfluid, inter-species interactions induce a nondissipative drag between the two superfluid flows (Andreev-Bashkin effect). We show that this behavior leads to a modification of the usual Berezinskii-Kosterlitz-Thouless (BKT) transition in two dimensions. We extend the renormalization of the superfluid densities at finite temperature using the renormalization group approach and find that the vortices of one component have a large influence on the superfluid properties of the other, mediated by the nondissipative drag. The extended BKT flow equations indicate that the occurrence of the vortex unbinding transition in one of the components can induce the breakdown of superfluidity also in the other, leading to a locking phenomenon for the critical temperatures of the two gases.

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“…The recent experimental realization of a mixture of Bose and Fermi superfluids in ultracold atoms has generated much interest in the properties of this new state of matter [1][2][3][4][5][6], and led to a surge of theoretical activity [7][8][9][10][11][12][13][14][15][16][17][18]. Collective excitations that characterize a system's response to small perturbations constitute one of the main sources of information for understanding the physics of many-body systems [19,20].…”

Section: Introductionmentioning

confidence: 99%

“…By examining the signs of the eigenvectors, one can identify the corresponding quadrupole modes of the Fermi and Bose superfluids. In contrast, the analytical results are shown by the solid lines, which are calculated from the expressions (14) combined with the analytical results for the dimensionless parameter and the mean square radii in appendix B. The positive (+) and negative (−) roots of the analytical expressions (14), as the frequencies of the harmonic trap for fermions are larger than bosons, actually correspond to the frequencies of the Fermi and Bose counterparts, respectively.…”

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“…In contrast, the analytical results are shown by the solid lines, which are calculated from the expressions (14) combined with the analytical results for the dimensionless parameter and the mean square radii in appendix B. The positive (+) and negative (−) roots of the analytical expressions (14), as the frequencies of the harmonic trap for fermions are larger than bosons, actually correspond to the frequencies of the Fermi and Bose counterparts, respectively. The frequencies of the quadrupole modes of the Bose and Fermi superfluid without interacting are also plotted by dashed lines for comparison.…”

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Collective oscillation modes of a superfluid Bose–Fermi mixture

Wen

Wang

2019

New J. Phys.

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In this work, we present a theoretical study for the collective oscillation modes, i.e. quadrupole, radial and axial mode, of a mixture of Bose and Fermi superfluids in the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a molecular Bose-Einstein condensate (BEC) in harmonic trapping potentials with cylindrical symmetry of experimental interest. To this end, we start from the coupled superfluid hydrodynamic equations for the dynamics of Bose-Fermi superfluid mixtures and use the scaling theory that has been developed for a coupled system. The collective oscillation modes of Bose-Fermi superfluid mixtures are found to crucially depend on the overlap integrals of the spatial derivations of density profiles of the Bose and Fermi superfluids at equilibrium. We not only present the explicit expressions for the overlap density integrals, as well as the frequencies of the collective modes provided that the effective Bose-Fermi coupling is weak, but also test the valid regimes of the analytical approximations by numerical calculations in realistic experimental conditions. In the presence of a repulsive Bose-Fermi interaction, we find that the frequencies of the three collective modes of the Bose and Fermi superfluids are all upshifted, and the change speeds of the frequency shifts in the BCS-BEC crossover can characterize the different groundstate phases of the Bose-Fermi superfluid mixtures for different trap geometries. superfluid mixtures of 7 Li-6 Li [1, 2], 41 K-6 Li [6], and 174 Yb-6 Li [5], and the Bose-Fermi interaction gives rise to a rich behavior. In the presence of a repulsive Bose-Fermi interaction, the frequencies of the dipole oscillations of the Bose and Fermi superfluids are both downshifted in the weakly confined direction [1,5,6], and the frequency shifts increase monotonically from the BCS side to the BEC side [48,49]. In contrast, the frequency in the tight confinement for the Bose superfluid is upshifted, whereas the frequency for the Fermi superfluid is still downshifted [6]. The frequency shifts show non-monotonic and resonantlike behaviors in both directions around the BCS side [6], which may be originated from the effects of fermionic pairs breaking [50].It is naturally to ask how Bose-Fermi interaction affects the collective modes of Bose and Fermi superfluids in the BCS-BEC crossover, which is of great interest recently. However, a theoretical study for the collective oscillation modes of Bose-Fermi superfluid mixtures in a realistic experimental situation is highly nontrivial. In this work, to study quadrupole, radial and axial modes in cylindrically symmetric traps, we start from the coupled superfluid hydrodynamic equations describing the dynamics of the Bose-Fermi superfluid mixtures. The scaling method for coupled systems is then applied, and the eigenvalue equations for the coupled collective modes are obtained, which are crucially sensitive to the overlap integrals of the spatial derivations of the Bose and Fermi densities at groundstate. To present the explicit expressio...

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Andreev–Bashkin effect in superfluid cold gases mixtures

Cited by 58 publications

References 48 publications

Quantum droplets of bosonic mixtures in a one-dimensional optical lattice

Quantum droplets of bosonic mixtures in a one-dimensional optical lattice

Coupled superfluidity of binary Bose mixtures in two dimensions

Collective oscillation modes of a superfluid Bose–Fermi mixture

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