Advertisement

Collective Excitations in Bose–Fermi Mixtures

  • Yoji Asano
  • Masato Narushima
  • Shohei Watabe
  • Tetsuro Nikuni
Article
  • 20 Downloads

Abstract

We investigate collective excitations of density fluctuations and a dynamic density structure factor in a mixture of Bose and Fermi gases in a normal phase. With decreasing temperature, we find that the frequency of the collective excitation deviates from that of the hydrodynamic sound mode. Even at a temperature much lower than the Fermi temperature, the collective mode frequency does not reach the collisionless limit analogous to zero sound in a Fermi gas, because of collisions between bosons and fermions.

Keywords

Bose–Fermi mixture Collective excitation Normal state First sound Zero sound Dynamic structure factor 

Notes

Acknowledgements

We are grateful to Y. Iijima for discussion in the early stage of this work. S.W. is supported by JSPS KAKENHI Grant Nos. (JP16K17774, JP18K03499), and T.N. is supported by JSPS KAKENHI Grant No. (JP16K05504).

References

  1. 1.
    R. Onofrio, Physics of our days: cooling and thermometry of atomic Fermi gases. Phys. Usp. 59(11), 1129 (2016)ADSCrossRefGoogle Scholar
  2. 2.
    R. Roy, R. Shrestha, A. Green, S. Gupta, M. Li, S. Kotochigova, A. Petrov, C.H. Yuen, Photoassociative production of ultracold heteronuclear \({\rm YbLi}^{*}\) molecules. Phys. Rev. A 94, 033413 (2016)ADSCrossRefGoogle Scholar
  3. 3.
    F. Scazza, G. Valtolina, P. Massignan, A. Recati, A. Amico, A. Burchianti, C. Fort, M. Inguscio, M. Zaccanti, G. Roati, Repulsive Fermi polarons in a resonant mixture of ultracold \(^{6}{\rm Li}\) atoms. Phys. Rev. Lett. 118, 083602 (2017)ADSCrossRefGoogle Scholar
  4. 4.
    B.J. DeSalvo, K. Patel, J. Johansen, C. Chin, Observation of a degenerate Fermi gas trapped by a Bose–Einstein condensate. Phys. Rev. Lett. 119, 233401 (2017)ADSCrossRefGoogle Scholar
  5. 5.
    X.C. Yao, H.Z. Chen, Y.P. Wu, X.P. Liu, X.Q. Wang, X. Jiang, Y. Deng, Y.A. Chen, J.W. Pan, Observation of coupled vortex lattices in a mass-imbalance Bose and Fermi superfluid mixture. Phys. Rev. Lett. 117, 145301 (2016)ADSCrossRefGoogle Scholar
  6. 6.
    R. Roy, A. Green, R. Bowler, S. Gupta, Two-element mixture of Bose and Fermi superfluids. Phys. Rev. Lett. 118, 055301 (2017)ADSCrossRefGoogle Scholar
  7. 7.
    C.J.E. Straatsma, V.E. Colussi, M.J. Davis, D.S. Lobser, M.J. Holland, D.Z. Anderson, H.J. Lewandowski, E.A. Cornell, Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap. Phys. Rev. A 94, 043640 (2016)ADSCrossRefGoogle Scholar
  8. 8.
    E. Arahata, T. Nikuni, Propagation of first and second sound in a highly elongated trapped Bose-condensed gas at finite temperatures. Phys. Rev. A 87, 033610 (2013)ADSCrossRefGoogle Scholar
  9. 9.
    S. Watabe, A. Osawa, T. Nikuni, Zero and first sound in normal Fermi systems. J. Low Temp. Phys. 158(5), 773 (2010)ADSCrossRefGoogle Scholar
  10. 10.
    M. Narushima, S. Watabe, K. Nikuni, Density and spin modes in imbalanced normal Fermi gases from collisionless to hydrodynamic regime. J. Phys. B At. Mol. Opt. Phys. 51(5), 055202 (2018)ADSCrossRefGoogle Scholar
  11. 11.
    L.A. Sidorenkov, M.K. Tey, R. Grimm, Y.H. Hou, L. Pitaevskii, S. Stringari, Second sound and the superfluid fraction in a Fermi gas with resonant interactions. Nature 498(7452), 78 (2013)ADSCrossRefGoogle Scholar
  12. 12.
    H. Hu, P. Dyke, C.J. Vale, X.J. Liu, First and second sound of a unitary Fermi gas in highly oblate harmonic traps. New J. Phys. 16(8), 083023 (2014)ADSCrossRefGoogle Scholar
  13. 13.
    A.A. Abrikosov, I.M. Khalatnikov, The theory of a Fermi liquid (the properties of liquid 3 He at low temperatures). Rep. Prog. Phys. 22(1), 329 (1959)ADSCrossRefGoogle Scholar
  14. 14.
    B.B. Hamel, Kinetic model for binary gas mixtures. Phys. Fluids 8(3), 418 (1965)ADSCrossRefGoogle Scholar
  15. 15.
    P. Capuzzi, P. Vignolo, F. Toschi, S. Succi, M.P. Tosi, Effects of collisions against thermal impurities in the dynamics of a trapped fermion gas. Phys. Rev. A 70, 043623 (2004)ADSCrossRefGoogle Scholar
  16. 16.
    L. Kadanoff, G. Baym, Quantum Statistical Mechanics (W.A. Benjamin Inc., New York, 1962)zbMATHGoogle Scholar
  17. 17.
    C.J. Pethick, H. Smith, Bose–Einstein Condensation in Dilute Gases (Cambridge university press, 2002)Google Scholar
  18. 18.
    J. Goldwin, S. Inouye, M.L. Olsen, D.S. Jin, Cross-dimensional relaxation in Bose–Fermi mixtures. Phys. Rev. A 71, 043408 (2005)ADSCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of PhysicsTokyo University of ScienceTokyoJapan

Personalised recommendations