{tag=Second-order phase transition}
{wiki}

The wiki comments: https://en.wikipedia.org/w/index.php?title=Ferromagnetism&oldid=965600553#Explanation
> The Bohr-van Leeuwen theorem, discovered in the 1910s, showed that classical physics theories are unable to account for any form of magnetism, including ferromagnetism. Magnetism is now regarded as a purely quantum mechanical effect. Ferromagnetism arises due to two effects from quantum mechanics: spin and the Pauli exclusion principle.


Ferromagnetism

{tag=Second-order phase transition}
{wiki}

= Superconductor
{synonym}

= Superconducting
{synonym}

Experiments:
* "An introduction to superconductivity" by Alfred Leitner originally published in 1965, source: http://www.alfredleitner.com/
* Isotope effect on the critical temperature. http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/coop.html mentions that:

  > If electrical conduction in mercury were purely electronic, there should be no dependence upon the nuclear masses. This dependence of the critical temperature for superconductivity upon isotopic mass was the first direct evidence for interaction between the electrons and the lattice. This supported the <BCS Theory> of lattice coupling of electron pairs.

\Video[http://youtube.com/watch?v=O_zjGYvP4Ps]
{title=20. Fermi gases, BEC-BCS crossover by Wolfgang Ketterle (2014)}
{description=Part of the "Atomic and Optical Physics" series, uploaded by <MIT OpenCourseWare>.}

Actually goes into the equations.

Notably, https://youtu.be/O_zjGYvP4Ps?t=3278 describes extremely briefly an experimental setup that more directly observes pair condensation.

\Video[http://youtube.com/watch?v=Yx666k2XH8E]
{title=Superconductivity and Quantum Mechanics at the Macro-Scale - 1 of 2 by Steven Kivelson (2016)}
{description=For the Stanford Institute for Theoretical Physics. Gives a reasonable basis overview, but does not go into the meat of BCS it at the end.}

\Video[https://www.youtube.com/watch?v=bD2M7P6dTVA]
{title=The Map of <Superconductivity> by <#Domain of Science>}
{description=Lacking as usual, but this one is particularly good as the author used to work on the area as he mentions in the video.}

Lecture notes:
* https://austen.uk/courses/tqm/superconductivity/

Media:
* http://www.supraconductivite.fr/en/index.php#supra-explication

  Cool CNRS video showing the condensed wave function, and mentioning that "every pair moves at the same speed". To change the speed of one pair, you need to change the speed of all others. That's why there's not energy loss.

Transition into superconductivity can be seen as a <phase transition>, which happens to be a <second-order phase transition>.


Superconductivity

{tag=Second-order phase transition}
{wiki}

= Superfluid
{synonym}

\Video[http://youtube.com/watch?v=7eZlF6IToQs]
{title=Alfred Leitner - Liquid Helium II the Superfluid by Alfred Leitner (1963)}
{description=Original source: http://www.alfredleitner.com[].}

\Video[http://youtube.com/watch?v=9FudzqfpLLs]
{title=Ben Miller experiments with superfluid helium by BBC (2011)}
{description=Just quickly shows the superfluid helium climbing out o the cup, no detailed setup. With https://www2.physics.ox.ac.uk/contacts/people/rtaylor[professor Robert Taylor] from the <University of Oxford>.}


Ciro Santilli @cirosantilli 37

 Tagged: Second-order phase transition