Exponential, rather than power-law, temperature dependence of the damping of a vibrating-wire resonator inA3at low temperatures

We have measured the damping of a vibrating-wire resonator in liquid ${}_{}{}^3{}_{}{}^{}\mathit{A}$ down to temperatures of ${\mathit{T}}_{\mathit{c}}$/T of 7 at zero bar pressure in a field of 500 mT. A simultaneous measurement of the damping in the B phase is also recorded. The response in the A phase is found to follow an exponential temperature dependence and not a power law as might be naively expected. This effect is a consequence of the exclusion of a large fraction of the bulk low-energy excitations from a surface by the bending of the texture.