Surface fluctuations of normal and superfluid He-3 probed by Wigner solid dynamics

Electron scattering from surface fluctuations on normal and superfluid He-3 has been measured by its effect on the linewidth of the low-wave-vector transverse magnetophonon mode of the electron crystal (the Wigner solid) floating on the helium surface. The relaxation rate becomes anomalously low below 70 mK, and reaches a plateau at about 3 times less than its expected value before dropping further at the superfluid transition. The absence of such anomalous behavior on He-4 suggests that the effect is specific to liquid He-3.