Superfluid helium-4
（重定向自Fountain Effect）
![Fig. 1. Phase diagram of ⁴He. In this diagram is also given the λ-line.](/Images/godic/202501/14/Phase_diagram_of_4He_01.svg5046.png")
![Fig. 2. Heat capacity of liquid 4He at saturated vapor pressure as function of the temperature. The peak at T=2.17 K marks a (second-order) phase transition.](/Images/godic/202501/14/Heat_capacity_of_4He_015046.jpg")
![Fig. 3. Temperature dependence of the relative superfluid and normal components ρn/ρ and ρs/ρ as functions of T.](/Images/godic/202501/14/Normal_and_superfluid_density_015046.jpg")
![Fig. 4. Helium II will](/Images/godic/202501/14/Helium-II-creep.svg5046.png")
Superfluid helium-4 is the superfluid form of helium-4, an isotope of the element helium. A superfluid is a state of matter in which the matter behaves like a fluid with zero viscosity. The substance, which looks like a normal liquid, flows without friction past any surface, which allows it to continue to circulate over obstructions and through pores in containers which hold it, subject only to its own inertia.