Dynamic Surface Properties of Liquid 3He Probed by Surface State Electrons

Two-dimensional (2D) electrons floating on the liquid He surface is a powerful tool to study the dynamic surface properties of both normal and superfluid 3 He. From the mobility measurement an evidence is found for the existence of ripplons on liquid 3 He at least above 140 mK. When the 2D electrons form a Wigner solid (WS) at low temperatures, they are accompanied with surface depression under each lattice site. Low frequency mobility of the WS probes the scattering of quasiparticles from the surface depression. The damping of high frequency magnetophonon resonances of the WS is dominated by the scattering of electrons from surface excitations. A comparative measurement on both 3 He and 4 He shows a prominent difference in the surface properties of 3 He from 4 He below 70 mK.