Collective modes and nonlinear acoustics in superfluid 3He-B

Author(s): R. H. McKenzie and J. A. Sauls
Comments: 2 Journal pages
Journal-ref: In ``Helium Three'', Volume 26, Chapter 5, pp. 255-311 of Modern Problems in Condensed Matter Physics, Eds. W. P. Halperin and L. P. Pitaevskii, Elsiever Science Publishers, The Netherlands, 1990.

We discuss the relationship of collisionless sound propagation and attenuation to the order parameter collective modes of superfluid 3He-B. These modes, which reflect the symmetries of the normal state as well as the broken gauge and relative rotational symmetries of the condensate, play a central role in the high-frequency acoustic response of the superfluid. We review the theory of acoustic spectroscopy based on the linear coupling of the J=2± modes. We develop the theory of the nonlinear acoustic response of superfluid 3He-B for the case of a three-wave resonance between two sound waves of different frequencies and the J=2± modes, as well as the generation of higher harmonic sound waves. The J=2+ modes couple nonlinearly to two zero-sound waves. The predictions for the nonlinear absorption and velocity anomalies resulting from the J=2+ modes depend on relatively well understood material properties of 3He.

Paper: [arXiv] [PDF]

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