Four and three-phonon scattering in isotropic superfluid helium

Автор(и)

  • I.N. Adamenko Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61077, Ukraine
  • Yu.A. Kitsenko Akhiezer Institute for Theoretical Physics National Science Center "Kharkov Institute of Physics and Technology" National Academy of Sciences of Ukraine, 1 Academicheskaya St., Kharkov 61108, Ukraine
  • K.E. Nemchenko Karazin Kharkov National University, 4 Svobody Sq., Kharkov 61077, Ukraine
  • A.F.G. Wyatt School of Physics, University of Exeter, Exeter EX4 4QL, UK

DOI:

https://doi.org/10.1063/1.3081151

Ключові слова:

superfluid helium, phonon scattering, dispersion curve, viscosity.

Анотація

We analyse the important role of four-phonon processes (4pp) in isotropic phonon systems of superfluid helium. The matrix elements and the rate of four-phonon processes are calculated. Special consideration is given to the 4pp in the momentum range where three-phonon processes are allowed. In this momentum range, we show that the 4pp scattering rate, at small angles, is equal to the scattering rate due to three-phonon processes. Then we show that the coefficient of first viscosity of superfluid helium is caused by two processes, the first is due to the transverse relaxation caused by many three-phonon processes and the second is due to four-phonon processes. The relaxation time that governs the viscosity is obtained from the sum of the rates from these two processes. The temperature dependence of the attenuation coefficient of a pulse of high-energy phonons in He II, due to scattering with thermal phonons, is also calculated. The theoretical results are compared with experimental data and found to be in good agreement.

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Опубліковано

2009-01-22

Як цитувати

(1)
Adamenko, I.; Kitsenko, Y.; Nemchenko, K.; Wyatt, A. Four and Three-Phonon Scattering in Isotropic Superfluid Helium. Fiz. Nizk. Temp. 2009, 35, 265-277.

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