T. M. Haard

Discovery of the acoustic Faraday effect in superfluid 3He-B

Acoustic waves provide a powerful tool for studying the structure of matter. For example, the speed, attenuation and dispersion of acoustic waves can give useful information on molecular forces and the microscopic mechanisms of absorption and scattering of acoustic energy. In solids, both compression and shear waves occur—longitudinal and transverse sound, respectively. But 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 helium-3 might support transverse sound waves at sufficiently low temperatures, the restoring forces for shear waves being supplied by the collective quantum behaviour of the particles in the fluid. Such shear waves will involve displacements of the fluid transverse to the direction of propagation, and so define a polarization direction similar to that of electromagnetic waves. Here we confirm experimentally the existence of transverse sound waves in superfluid 3He-B by observing the rotation of the polarization of these waves in the presence of a magnetic field. This phenomenon is the acoustic analogue of the magneto-optic Faraday effect, whereby the polarization direction of an electromagnetic wave is rotated by a magnetic field applied along the propagation direction.

Strong coupling corrections to the Ginzburg-Landau theory of superfluid He3

In the Ginzburg-Landau theory of superfluid

The pathlength distribution of simulated aerogels

^{3}\mathrm{He}

Specific heat of disordered superfluid 3He.

, the free energy is expressed as an expansion of invariants of a complex order parameter. Strong coupling effects, which increase with increasing pressure, are embodied in the set of coefficients of these order-parameter invariants [A. J. Leggett, Rev. Mod. Phys. 47, 331 (1975); E. V. Thuneberg, Phys. Rev. B 36, 3583 (1987); J. Low Temp. Phys. 122, 657 (2001)]. Experiments can be used to determine four independent combinations of the coefficients of the five fourth-order invariants. This leaves the phenomenological description of the thermodynamics near

Acoustics of a “Dirty” Fermi Liquid: 3He in Aerogel

{T}_{c}

First- and zero-sound velocity and fermi liquid parameter F2s in liquid3He determined by a path length modulation technique

incomplete. Theoretical understanding of these coefficients is also quite limited. We analyze our measurements of the magnetic susceptibility and the NMR frequency shift in the

New NMR evidence: Can an axi-planar superfluid3He-A order parameter be ruled out?

B

Nuclear magnetic resonance of {sup 3}He superfluid confined in high porosity aerogel

phase which refine the four experimental inputs to the phenomenological theory. We propose a model based on existing experiments, combined with calculations by Sauls and Serene [Phys. Rev. B 24, 183 (1981)] of the pressure dependence of these coefficients, in order to determine all five fourth-order terms. This model leads us to a better understanding of the thermodynamics of superfluid

High frequency acoustic measurements in liquid3He near the transition temperature

^{3}\mathrm{He}

NMR on superfluid3He in aerogel

in its various states. We discuss the surface tension of bulk superfluid