16:58 Thursday 11 July 2019 JST
Interesting to talk about the Meisner effect and flux pinning at SCC today. I have always assumed I understand the meaning based on the English presentation, but I felt a bit unsure when I was breaking it down in detail for Yasu as he was practicing his explanation of the same.
My understanding: when a superconductor is below its critical temperature it pushes (almost) all magnetic flux out of itself. This is the Meisner effect, apparently named after a scientist named Meisner.
Impurities in the superconductor mean some lines of magnetic flux pierce the superconductor and the superconductor “remembers” the strength and direction of those lines and pins itself to them. This is called flux pinning, apparently not named after a scientist.
What is this “memory”? I guess while the material is not a superconductor, magnetic flux pierces it like any other non-ferrous material. As it becomes superconducting as it passes below its critical temperature the flux already passing through it are… what exactly?
(( I wonder if electrical resistance in normal conductors is what causes the magnetic fields??? hmmm ))