My misconception was that electrons were present in a BEC. However, how do fermions behave in low temperature and how does it differ from the behaviour of bosons?


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    $\begingroup$ In a Bose-Einstein condensate you have no electrons, only bosons. In a superconductor you have electrons which form Cooper pairs. $\endgroup$ – Lars Milz Dec 16 '16 at 18:18
  • $\begingroup$ So when forming a BEC, how does a substance lose the electron? $\endgroup$ – Zwolf Dec 16 '16 at 18:20
  • $\begingroup$ I think you'll have to be a bit more specific. At the moment it's unclear what you are asking. $\endgroup$ – John Rennie Dec 16 '16 at 18:21
  • $\begingroup$ Are you asking about the electron clouds of neutral atoms forming a BEC? The edited question is completely different from the original, by the way. $\endgroup$ – Mark Mitchison Dec 16 '16 at 18:25
  • $\begingroup$ My misconception arised from reading about how BEC behaves as a 'superatom'. Thank you for the clarification s $\endgroup$ – Zwolf Dec 16 '16 at 18:26

Electron are spin 1/2 particles, and hence are fermions.

Fermions do not have a Bose-Einstein condensate phase (that is, as the name suggests, for bosons).

In some particular situation (low temperature etc) they can give rise to a Bose-Einstain condensate if they couple and form bosonic two-electron states (Cooper pairs) but then it is really the couples that form a condensate, rather than the electrons


In general (an other example are alpha particles, that are bosons but made of nucleons that are fermions) as long as you are in conditions such that you can ignore the internal structure of the bosonic composite you can have a Bose-Einstein condensate.

Addendum II because the OP changed radically the question:

Electrons are fermions; fermions have antisymmetric wavefunction, that is, if the system have discrete energy levels, thy are subjected to Pauli exclusion principle, and therefore two electrons cannot occupy the same level.

Bosons, on the other hand, can "collapse" to the lowest energy level and this is the BE condensate

  • $\begingroup$ Why do fermions not have a BEC phase? $\endgroup$ – Zwolf Dec 16 '16 at 18:30
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    $\begingroup$ Because only bosons could form a BEC. For fermions it is possible that they form Cooper pairs and with this we have superconductivity. $\endgroup$ – Lars Milz Dec 16 '16 at 18:33
  • $\begingroup$ I edited the answer to touch that issue $\endgroup$ – yoric Dec 16 '16 at 18:33
  • $\begingroup$ My question was based on a serious misconception and hence, had to be changed. One more question: Does the matter need to be anionic in order to form a BEC or can it be done using a neutral atom? $\endgroup$ – Zwolf Dec 16 '16 at 18:39
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    $\begingroup$ I am not sure of what you are asking now; bosons can for BEC whereas fermions cannot. If you are considering a composite "particle" (like an atom, an alpha particle, a Cooper pair) that as a whole acts like a boson, it can condensate, but this is meaningful until you can consider the atom as a whole; if the conditions (energy, temperature etc) are such that the internal structure of your composite object becomes relevant than you are not talking about the composite object anymore $\endgroup$ – yoric Dec 16 '16 at 18:44

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