Discovery of the Acoustic Faraday Effect in Superfluid 3He-B

Author(s): Y. Lee, T. M. Haard, W. P. Halperin and J. A. Sauls
Comments: 4 pages with 3 figures
Journal: Nature 400, 431 (1999) [DOI] [Press Release]
Acoustic waves provide a powerful tool for studying the structure of matter. The speed, attenuation and dispersion of acoustic waves give useful details of the molecular forces and microscopic mechanisms for absorption and scattering of acoustic energy. In solids both compressional and shear waves occur, so-called longitudinal and transverse sound. However, normal liquids do not support shear forces and consequently transverse waves do not propagate in liquids with one notable exception. In 1957 Landau predicted that the quantum liquid phase of 3He might exhibit transverse sound at sufficiently low temperatures where the restoring forces for shear waves are supplied by the collective action of the particles in the fluid. Shear waves in liquid 3He involve displacements of the fluid transverse to the direction of propagation. The displacement defines the polarization direction of the wave similar to electromagnetic waves. We have observed rotation of the polarization of transverse sound waves in superfluid 3He-B in a magnetic field. This magneto-acoustic effect is the direct analogue to the magneto-optical effect discovered by Michael Faraday in 1845,where the polarization of an electromagnetic wave is rotated by a magnetic field along the propagation direction.

Paper: [PDF] [HTML] [arXiv]

Index Return to index