3.F.2. Liquid He3

He3 has only 3/4 of the mass of He4.  Hence,

        T Boiling [H e 3 ]= 3 4 T Boiling [H e 4 ]             P Solidification [H e 3 ]= 4 3 P Solidification [H e 4 ]

The phase diagram of He3 is shown in 2 scales in Figs.3.17-8.

 

The minimum in the l-s coexistence curve in Fig.3.17 is due to the spin contribution to the entropy which makes ΔS= S liquid S solid  change sign at T0.3K .  Since ΔVconst  along the coexistence curve, the minimum follows directly from the Clausius- Clapeyron equation ( dP dT ) coex = TΔS ΔV .

 

The superfluid phases (see Fig.3.18) appears only for T0.0027K  so that they are not discernible in Fig.3.17.  Since He3 is a fermion, a (Bose-Einstein) condensation into the superfluid phase requires a pairing mechanism.  Depending on the angular momenta of the bounded pairs, different superfluid phases results.

1.         The high temperature A-phase is anisotropic.

2.         The low temperature B-phase is more or less isotropic.

3.         A third phase appears under magnetic field.

4.         Transition between normal & superfluid is continuous.

5.         Transition between the A and B phases is 1st order.