Manipulation of $\hat l$ Texture by Counterflow in Superfluid ³He A₁

Abstract

A rectangular resonator chamber is fitted with three pairs of second sound transducers for studying the spin-entropy wave propagation in ³ He A ₁. The anisotropy in the spin-entropy wave propagation velocity is unambiguously established by simultaneously measuring the modes propagating in both parallel and perpendicular directions to the applied magnetic field. The anisotropic $\hat l$ texture within the cell is ”manipulated” by introducing oscillatory counterflows with one transducer. The manipulated texture is monitored by measuring the resonant mode with the pair of transducers which are orthogonal to the drive transducer. The manner of texture manipulation depends on both the amplitude and frequency of the drive. In some cases, the observed changes in texture are abrupt and hysteretic. The texture transitions may be of first order.