Thermomechanical Effect in Normal Liquid 3He with Non-Magnetic Boundary Scattering

The thermomechanical effect in normal liquid3He, confined in a porous plug pre-plated with 44He non-magnetic monolayers, has been measured. A previous experiment showed that there is a thermomechanical effect (analogue of thermoelectricity) but only when the3He is confined in pores with d ≪ l, where d is the pore size and l the bulk3He quasiparticle mean free path. The effect was large, an order of magnitude larger than a theoretical determination by Edwards, Culman and He. This was possibly a magnetic scattering anomaly; we therefore repeated the experiment with the pre-plated porous plug, with dramatically different results. In the d ≪ l limit, below 5 mK, we find dP/dT ∼ S/6, compared with the theoretical S/3, where S is the entropy per unit volume.