Since superfluids consists of integer spin bosons or effective bosonic Cooper-paired fermions, Pauli Exclusion Principle does not apply to them. They can thus occupy the same quantum state as any other normal baryonic matter, effectively going through them if electromagnetic repulsion between them is low enough to not oppose its motion.

Basically, if a superfluid and a slab of cold baryonic matter meets, will the superfluid go through the baryonic matter unaffected with little interaction? (Assuming it has enough velocity to overcome the electromagnetic repulsion i.e. $KE \space> EPE$)

For example He-4 is bosonic as it has an integer spin 0, if we cool it down to superfluid temperature and put it in a container made of baryonic matter (i.e. glass/silicon dioxide) it will pass through the container? (Since it can occupy same quantum states as the particles in the container.)

Rather creepy theory, don't you think?

P.S. : Quantum state includes spatial coordinates of the wave function of the particle and spin and other things, so Pauli Exclusion forbids fermions to occupy the same space unless their spin is opposite. This does not apply to spin 0 particles (bosons) so they can all occupy the same space if there was no repulsion between them. So spin 0 particles can pass freely through fermions and other particles if the EM repulsion between them is overcome either due to it being weak or the condensates having high velocity?

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    $\begingroup$ I'm not sure I understand the question, given that it is rather easy to find the strange behaviour (which is not "passing through", but creeping along the surface) superfluid Helium exhibits in containers. And even in the absense of the Pauli exclusion principle, you still have electromagnetic repulsion. $\endgroup$
    – ACuriousMind
    Jul 20, 2016 at 15:33
  • $\begingroup$ @Lagrangian Re what liquid-helium does if one puts it in a glass container, "(which is not 'passing through', but creeping along the surface)": I made that same mistake after viewing a youtube-video: it certainly does LOOK like it's going thru the glass !! $\endgroup$ Jul 20, 2016 at 17:50

1 Answer 1


So spin 0 particles can pass freely through fermions and other particles if there is lack of EM repulsion between them?

There is never lack of EM repulsion because baryonic matter is made of charged particles. The superfluid will stay into the container.

  • $\begingroup$ And if we apply enough force to overcome the electromagnetic repulsion, they do go to the same coordinates, strong force will do something to it? $\endgroup$
    – Lagrangian
    May 16, 2017 at 5:10
  • $\begingroup$ In principle yes, but if you calculate the electromagnetic force involved between, say protons you will find that there is almost no way to overcome it $\endgroup$
    – Dimitri
    May 16, 2017 at 12:20

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