SPECIFIC-HEAT OF LIQUID-HE-3 UNDER PRESSURE IN A RESTRICTED GEOMETRY

We have investigated the specific heat of liquid He-3 confined to an A g sinter with an average pore size of about 1000 Angstrom in the tempe rature range 1 mK less than or equal to T less than or equal to 20 mK and at pressures 4.8 bar less than or equal to p less than or equal to 34.0 bar. The specific heat of normal-fluid He-3 in the sinter ports shows the linear temperature dependence expected for a Fermi liquid. H owever, the effective mass of the He-3 quasiparticles is clearly enhan ced in the restricted geometry compared to data obtained in bulk He-3. In addition, there is a temperature-independent contribution to the s pecific heat, the origin of which can be interpreted as the specific h eat of the second layer of He-3 on the Ag surface. Moreover, compared with the results obtained for bulk He-3, we observe a much broader max imum in the specific heat in the vicinity of the superfluid transition ; this maximum occurs about 0.4 mK below the bulk superfluid transitio n temperature. Furthermore, in the confinement of the sinter only a pa rt of the He-3 in the sinter (about 60%) becomes superfluid. In contra st to the results obtained with pure 3He the specific heat of a liquid He-3-He-4 mixture (1% He-3) in the Ag sinter shows no deviation from bulk data.