Neutron Spin Echo Observation of Spontaneous Phonon Decay in Superfluid 4He

  • F. Mezei
  • C. Lartigue
  • B. Farago
Part of the NATO ASI Series book series (NSSB, volume 257)


Due to the peculiar shape of the phonon-roton dispersion curve in 4He, the spontaneous decay of one excitation into a number of others is forbidden for wavenumbers above qc ≃ 0.55 Å−1. Therefore, q > qc excitations can only decay by scattering on another, thermal excitation, and consequently, in the ground state T→ 0 their lifetime becomes infinite, as put to evidence by ballistic photon/roton experimentsl. In contrast the q ≤ qc phonons must have a finite lifetime at T→ 0 and we shall present the first quantitative observation of this phenomenon.


Thermal Excitation Spontaneous Decay Neutron Spin Finite Lifetime Quantitative Observation 
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  1. 1.
    A. F. G. Wyatt, in this volume and references therein.Google Scholar
  2. 2.
    F. Mezei, The Principle of Neutron Spin Echo, in: “Neutron Spin Echo”, F. Mezei, ed., Springer Verlag Heidelberg (1980).Google Scholar
  3. 3.
    F. Mezei and W. G. Stirling, Neutron Scattering study of the lifetime of phonons in superfluid 4He, 75th Jubilee Conf. on 4He, J.G.M. Armitage, ed., World Scientific, Singapore (1983).Google Scholar
  4. 4.
    H.J. Maris, Phonon-phonon interactions in liquid helium, Rev. Mod. Phys. 49: 341 (1977).ADSCrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • F. Mezei
    • 1
  • C. Lartigue
    • 1
  • B. Farago
    • 1
    • 2
  1. 1.Hahn-Meitner-InstitutBerlin 39Germany
  2. 2.Institut Laue-Langevin, 156XGrenoble CedexFrance

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