Observation of a Textural Transformation Associated with the <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>A</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> Transition in Superfluid <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mmultiscripts><mrow><mi mathvariant="normal">He</mi></mrow><mprescripts></mprescripts><mrow></mrow><mrow><mn>3</mn></mrow><mrow></mrow><mrow></mrow></mmultiscripts></mrow><mo>−</mo><mi>A</mi></math></span>

P. G. N. de Vegvar; R. Movshovich; E. L. Ziercher; D. M. Lee

doi:10.1103/PhysRevLett.57.1028

Observation of a Textural Transformation Associated with the $A_{2}$ Transition in Superfluid ${}^{3}{He} - A$

P. G. N. de Vegvar, R. Movshovich, E. L. Ziercher, and D. M. Lee

Phys. Rev. Lett. 57, 1028 – Published 25 August 1986

Abstract

We have observed an anomaly in the attenuation and phase velocity of zero sound in superfluid ${}^{3}{He} - A$ at a temperature experimentally unresolvable from the $A_{2}$ transition. The feature is present at all magnetic fields and frequencies for sound propagated perpendicular to the applied field H, but it disappears for sound traveling along H. We discuss this phenomenon in terms of a first-order transformation between dipole-locked and dipole-unlocked planar textures driven by the thermodynamic second-order phase transition at $T_{A_{2}}$ . We also report the first observed splitting of the normal flapping mode in a magnetic field.