Specific heat of liquid3Heunder pressure in a restricted geometry

Abstract

We have investigated the specific heat of liquid 3 He confined to an Ag sinter with an average pore size of about 1000 Å in the temperature range 1 mKрTр20 mK and at pressures 4.8 barр pр34.0 bar. The specific heat of normal-fluid 3 He in the sinter pores shows the linear temperature dependence expected for a Fermi liquid. However, the effective mass of the 3 He quasiparticles is clearly enhanced in the restricted geometry compared to data obtained in bulk 3 He. In addition, there is a temperature-independent contribution to the specific heat, the origin of which can be interpreted as the specific heat of the second layer of 3 He on the Ag surface. Moreover, compared with the results obtained for bulk 3 He, we observe a much broader maximum in the specific heat in the vicinity of the superfluid transition; this maximum occurs about 0.4 mK below the bulk superfluid transition temperature. Furthermore, in the confinement of the sinter only a part of the 3 He in the sinter ͑about 60%͒ becomes superfluid. In contrast to the results obtained with pure 3 He the specific heat of a liquid 3 He-4 He mixture ͑1% 3 He͒ in the Ag sinter shows no deviation from bulk data.

Heat capacity of liquid3Hein sintered silver powder

“…2 In contrast to the past results Schrenk and König reported the new result that the constant heat capacity in the silver sinter is several times as large as the constant heat capacity in the Vycor glass. 4 They presented new issues of whether the constant heat capacity depends on the substrate, i.e., silver or Vycor, and whether it depends on liquid or solid. We intend to resolve these issues by measuring the heat capacity for both the liquid and solid 3 He on the same substrate.…”

Surface Specific Heat ofHe3and Andreev Bound States

“…For measurements of the heat capacity this latter approach is preferable. Earlier experiments [20,21,22] of this kind show that the heat capacity differs from that of the bulk, without a consensus for interpretation. Greywall suggested that there is a healing length of the superfluid at the surface [20].…”

“…Greywall suggested that there is a healing length of the superfluid at the surface [20]. Others have argued [21,22] that there is a broad distribution of transition temperatures of disconnected superfluid regions. In our experiment we use a high resolution temperature sweep method that can provide sufficient detail to explore the temperature and 3 He obtained from a slow warm up trace at 11.31 bar.…”