Quasiparticle Interactions in Two - Dimensional 3 He on 4 He Films

M. Dann, J. Nyéki,* B. P. Cowan, and J. Saunders Millikelvin Laboratory, Department of Physics, Royal Holloway University of London, Egham, Surrey, TW20 0EX, United Kingdom (Received 28 January 1999) Measurements are reported of the heat capacity of 3He bound to an atomically layered 4He film on the surface of graphite. At 3He coverages n3 , 4 nm22, the 3He forms a uniform 2D Fermi system. Thereafter with increasing n3 we resolve two steps in the heat capacity, each arising from the formation of a further 2D continuum built on excited surface-normal states. We infer information on the hydrodynamic mass, quasiparticle interactions, and energetics of these states. Both short range repulsive interactions and ripplon mediated quasiparticle interactions are important. [S0031-9007(99)09131-0]