Experiments on Orbital Dynamics in SuperfluidHe3-A

The response of the orbital degrees of freedom of superfluid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ to a magnetic field suddenly rotated through a small angle is a decaying exponential rather than an oscillatory response. Analysis of the field and temperature dependence of the time constant supports the Cross-Anderson orbital-viscosity theory as complemented by the Pethick-Smith relaxation-time theory but reveals a discrepancy in the susceptibility-anisotropy energy near $T_c$.