Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1607.03221 · Physical Review Letters

Two-Element Mixture of Bose and Fermi Superfluids

Richard Roy, Alaina Green, R. Bowler, Subhadeep Gupta

Published Feb 2, 2017• 113 citations
arXivHTMLPDF

Abstract

We report on the production of a stable mixture of bosonic and fermionic superfluids composed of the elements ^{174}Yb and ^{6}Li which feature a strong mismatch in mass and distinct electronic properties. We demonstrate elastic coupling between the superfluids by observing the shift in dipole oscillation frequency of the bosonic component due to the presence of the fermions. The measured magnitude of the shift is consistent with a mean-field model and its direction determines the previously unknown sign of the interspecies scattering length to be positive. We also observe the exchange of angular momentum between the superfluids from the excitation of a scissors mode in the bosonic component through interspecies interactions. We explain this observation using an analytical model based on superfluid hydrodynamics.

DOI
10.1103/physrevlett.118.055301

Related papers

Coupled dipole oscillations of a mass-imbalanced Bose-Fermi superfluid mixture

Yu-Ping Wu, Xing-Can Yao, Xiangpei Liu +6 more

Recent experimental realizations of superfluid mixtures of Bose and Fermi quantum gases provide a unique platform for exploring diverse superfluid phenomena. We study dipole oscillations of a double superfluid in a cigar-shaped optical dipole trap, consisting of $^{41}\mathrm{K}$ and $^{6}\mathrm{Li}$ atoms with a large mass imbalance, where the oscillations of the bosonic and fermionic components are coupled via the Bose-Fermi interaction. In our high-precision measurements, the frequencies of both components are observed to be shifted from the single-species ones, and exhibit unusual features. The frequency shifts of the $^{41}\mathrm{K}$ component are upward (downward) in the radial (axial) direction, whereas the $^{6}\mathrm{Li}$ component has downshifted frequencies in both directions. Most strikingly, as the interaction strength is varied, the frequency shifts display a resonantlike behavior in both directions, for both species, and around a similar location at the BCS side of the fermionic superfluid. These rich phenomena challenge the theoretical understanding of superfluids.

arXiv:1705.04496•Physical review. B./Physical review. B•Jan 22, 2018•30 citations

A mixture of Bose and Fermi superfluids

Igor Ferrier-Barbut, Marion Delehaye, Sébastien Laurent +5 more

Superconductivity and superfluidity of fermionic and bosonic systems are remarkable many-body quantum phenomena. In liquid helium and dilute gases, Bose and Fermi superfluidity has been observed separately, but producing a mixture in which both the fermionic and the bosonic components are superfluid is challenging. Here we report on the observation of such a mixture with dilute gases of two lithium isotopes, lithium-6 and lithium-7. We probe the collective dynamics of this system by exciting center-of-mass oscillations that exhibit extremely low damping below a certain critical velocity. Using high-precision spectroscopy of these modes, we observe coherent energy exchange and measure the coupling between the two superfluids. Our observations can be captured theoretically using a sum-rule approach that we interpret in terms of two coupled oscillators.

arXiv:1404.2548•Science•Jul 18, 2014•293 citations

Dipole Oscillation in a Bose–Fermi Superfluid Mixture of 41 K and 6 Li

Ren Zhang

We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose–Fermi superfluid mixture. Our results show that the Λ transition occurs in such a system, which interprets the perplexing phenomenon observed in the recent experiment [arXiv:1705.04496]. In that experiment, the frequency shift of the bosonic gas was measured with different fermion-fermion s-wave scattering lengths a f . The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around 1/ k F a f ≃ −0.2 with k F being the Fermi momentum. In the present work, the relation between the bosonic frequency shift and the compressibility of the Fermi gas is revealed by means of the equation of state of the superfluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a Λ-like shape around 1/ k F a f ≃ −0.2. We would like to stress that no free parameter is used in our calculation and our results can be further testified in a future experiment.

Chinese Physics Letters•Apr 1, 2018•2 citations

Induced interactions in a superfluid Bose-Fermi mixture

J. J. Kinnunen, Georg M. Bruun

We analyze a Bose-Einstein condensate (BEC) mixed with a superfluid two-component Fermi gas in the whole BCS-BEC crossover. Using a quasiparticle random-phase approximation combined with Beliaev theory to describe the Fermi superfluid and the BEC, respectively, we show that the single-particle and collective excitations of the Fermi gas give rise to an induced interaction between the bosons, which varies strongly with momentum and frequency. It diverges at the sound mode of the Fermi superfluid, resulting in a sharp avoided crossing feature and a corresponding sign change of the interaction energy shift in the excitation spectrum of the BEC. In addition, the excitation of quasiparticles in the Fermi superfluid leads to damping of the excitations in the BEC. Besides studying induced interactions themselves, we can use these prominent effects to systematically probe the strongly interacting Fermi gas.

arXiv:1502.00402•Physical Review A•Apr 30, 2015•42 citations

Calibration of the interaction energy between Bose and Fermi superfluids

Ren Zhang, Wei Zhang, Hui Zhai +1 more

In this paper we study the interaction energy in a mixture of Bose and Fermi superfluids realized in recent cold atom experiments. On the Bose-Einstein-condensate (BEC) side of a Feshbach resonance between fermionic atoms, this interaction energy can be directly related to the scattering length between a bosonic atom and a dimer composed of fermions. We calculate the atom-dimer scattering length from a three-body analysis with both a zero-range model and a separable model, including the van der Waals length scale, and we find significant deviation from the result given by a mean-field approach. We also find that the multiple scattering between atom and dimer can account for such a deviation. Our results provide a calibration to the mean-field interaction energy, which can be verified by measuring the shift of collective oscillation frequency.

arXiv:1409.0282•Physical Review A•Dec 8, 2014•36 citations

Dipole dynamics of an interacting bosonic mixture

Luca Cavicchioli, C. Fort, Michele Modugno +2 more

We unravel the coupled dipole dynamics of a two-species Bose-Einstein condensate with tunable interspecies interaction. We produce a degenerate mixture of $^{41}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ in an optical trap and we study the dipole oscillations of both atomic species in the linear response regime. Varying the interspecies interaction from the weakly to the strongly attractive side, we measure the frequencies and the composition of the two dipole eigenmodes. For sufficiently strong interactions, even beyond the mean-field collapse, we find that the frequency of the low-energy eigenmode is determined only by the bare trap frequencies and the species population imbalance. The experimental results are well reproduced by numerical simulations based on two coupled Gross-Pitaevskii equations. Our findings provide a detailed picture of the dipole excitations in asymmetric bosonic mixtures.

arXiv:2207.13599•Physical Review Research•Oct 31, 2022•17 citations
We report on the production of a stable mixture of bosonic and fermionic superfluids composed of the elements ^{174}Yb and ^{6}Li which feature a strong mismatch in mass and distinct electronic properties. We demonstrate elastic coupling between the superfluids by observing the shift in dipole oscillation frequency of the bosonic component due to the presence of the fermions. The measured magnitude of the shift is consistent with a mean-field model and its direction determines the previously unknown sign of the interspecies scattering length to be positive. We also observe the exchange of angular momentum between the superfluids from the excitation of a scissors mode in the bosonic component through interspecies interactions. We explain this observation using an analytical model based on superfluid hydrodynamics.
Recent experimental realizations of superfluid mixtures of Bose and Fermi quantum gases provide a unique platform for exploring diverse superfluid phenomena. We study dipole oscillations of a double superfluid in a cigar-shaped optical dipole trap, consisting of 41K^{41}\mathrm{K}41K and 6Li^{6}\mathrm{Li}6Li atoms with a large mass imbalance, where the oscillations of the bosonic and fermionic components are coupled via the Bose-Fermi interaction. In our high-precision measurements, the frequencies of both components are observed to be shifted from the single-species ones, and exhibit unusual features. The frequency shifts of the 41K^{41}\mathrm{K}41K component are upward (downward) in the radial (axial) direction, whereas the 6Li^{6}\mathrm{Li}6Li component has downshifted frequencies in both directions. Most strikingly, as the interaction strength is varied, the frequency shifts display a resonantlike behavior in both directions, for both species, and around a similar location at the BCS side of the fermionic superfluid. These rich phenomena challenge the theoretical understanding of superfluids.
Superconductivity and superfluidity of fermionic and bosonic systems are remarkable many-body quantum phenomena. In liquid helium and dilute gases, Bose and Fermi superfluidity has been observed separately, but producing a mixture in which both the fermionic and the bosonic components are superfluid is challenging. Here we report on the observation of such a mixture with dilute gases of two lithium isotopes, lithium-6 and lithium-7. We probe the collective dynamics of this system by exciting center-of-mass oscillations that exhibit extremely low damping below a certain critical velocity. Using high-precision spectroscopy of these modes, we observe coherent energy exchange and measure the coupling between the two superfluids. Our observations can be captured theoretically using a sum-rule approach that we interpret in terms of two coupled oscillators.
We study the relation between the bosonic frequency shift of a dipole oscillation and the fermionic compressibility in a Bose–Fermi superfluid mixture. Our results show that the Λ transition occurs in such a system, which interprets the perplexing phenomenon observed in the recent experiment [arXiv:1705.04496]. In that experiment, the frequency shift of the bosonic gas was measured with different fermion-fermion s-wave scattering lengths a f . The most striking feature of their measurement is that the frequency shift shows a puzzling non-monotonic behavior around 1/ k F a f ≃ −0.2 with k F being the Fermi momentum. In the present work, the relation between the bosonic frequency shift and the compressibility of the Fermi gas is revealed by means of the equation of state of the superfluid mixture. Making use of the relation, we find that the compressibility of Fermi gas shows a Λ-like shape around 1/ k F a f ≃ −0.2. We would like to stress that no free parameter is used in our calculation and our results can be further testified in a future experiment.
We analyze a Bose-Einstein condensate (BEC) mixed with a superfluid two-component Fermi gas in the whole BCS-BEC crossover. Using a quasiparticle random-phase approximation combined with Beliaev theory to describe the Fermi superfluid and the BEC, respectively, we show that the single-particle and collective excitations of the Fermi gas give rise to an induced interaction between the bosons, which varies strongly with momentum and frequency. It diverges at the sound mode of the Fermi superfluid, resulting in a sharp avoided crossing feature and a corresponding sign change of the interaction energy shift in the excitation spectrum of the BEC. In addition, the excitation of quasiparticles in the Fermi superfluid leads to damping of the excitations in the BEC. Besides studying induced interactions themselves, we can use these prominent effects to systematically probe the strongly interacting Fermi gas.
In this paper we study the interaction energy in a mixture of Bose and Fermi superfluids realized in recent cold atom experiments. On the Bose-Einstein-condensate (BEC) side of a Feshbach resonance between fermionic atoms, this interaction energy can be directly related to the scattering length between a bosonic atom and a dimer composed of fermions. We calculate the atom-dimer scattering length from a three-body analysis with both a zero-range model and a separable model, including the van der Waals length scale, and we find significant deviation from the result given by a mean-field approach. We also find that the multiple scattering between atom and dimer can account for such a deviation. Our results provide a calibration to the mean-field interaction energy, which can be verified by measuring the shift of collective oscillation frequency.
We unravel the coupled dipole dynamics of a two-species Bose-Einstein condensate with tunable interspecies interaction. We produce a degenerate mixture of $^{41}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ in an optical trap and we study the dipole oscillations of both atomic species in the linear response regime. Varying the interspecies interaction from the weakly to the strongly attractive side, we measure the frequencies and the composition of the two dipole eigenmodes. For sufficiently strong interactions, even beyond the mean-field collapse, we find that the frequency of the low-energy eigenmode is determined only by the bare trap frequencies and the species population imbalance. The experimental results are well reproduced by numerical simulations based on two coupled Gross-Pitaevskii equations. Our findings provide a detailed picture of the dipole excitations in asymmetric bosonic mixtures.