Liquid mixture of ³He and ⁴He

Phase diagram for the mixture of helium isotopes, ³He and ⁴He. Pure liquid ⁴He enters into the superfluid phase at 2.17 K (left in the figure). The presence of ³He shifts the superfluid transition to lower temperatures. If the liquid has sufficiently ³He, a phase separation takes place at low temperatures. Near zero temperature the ⁴He-rich phase contains at most 6% of ³He (lower left corner). The other phase consists of essentially pure ³He (lower right corner). Also the latter phase enters superfluid state but at a much lower temperature, which is not visible in the figure.

Note that the figure and the numbers above correspond to saturated vapor pressure, and are functions of pressure.

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