Originally posted by Count Iblis II:
The arguments based on London theory which uses the order parameter is pretty simple. They are not real derivations because by writing down the effective theory you almost put in the effect by hand. This is similar to the Higgs effect: Photons become effectively massive and em-fields don't propagate inside the superconductor.
I'm talking about a derivation from a funbdamental theory like BCS theory, see e.g. here.
You can't just say: Let's assume that the electrons don't scatter. Then you also put in the desired result in by hand. You have to start from some realistic microscopic model that describes the electrons in the metal and then show that you indeed have the Meissner effect. This is done in the book by Rickayzen (and in many other books, but I happened to have read that book). Firstly the BCS theory IS NOT a fundamental theory. It is only descriptive because it cannot be used to predict what one should do to a material in order to make it superconductive (As Pauli would have remarked: "It is not even wrong"). This has been pointed out by many experimentalists that worked on superconduction; I rather believe experiment than an "advanced theory" which you are clearly not capable of understanding to such an extent that you can explain it in terms of the physics involved.
Secondly you keep on bringing in the Meissner effect into the discussion. It has nothing to do with this thread. If you go back to your undergraduate books (which I recommend that you do before reading books with "advanced mathematics" which you are clearly not able to explain in terms of physics) you will realise that Kamerlingh-Onnes generated non-dissipative circular currents at least 15 years before the Meissner effect was discovered. To generate these currents by switching on a magnetic field that increases to a maximum value so that an opposite and equal magnetic field is established such that the currents keep on going, proves zero resistance and NOT that the material is a perfect diamagnet.The Meissner effect manifests when a static magnetic field is established before cooling the superconductor through its critical temperature. It was expected from basic electrodynamics that the magnetic field within the material will become trapped as soon as the material becomes superconducting. It was thus a great surprise when the material expelled the field.
Since I started this discussion I discussed the situation when a magnetic field is switched on to increase over a material that is already in the superconducting state. This IS NOT the Meissner effect; but for some strange reason you are unable to understand this simple fact. Please go back to your undergraduate books and FIRST try and understand them before trying to meddle with "advanced mathematics" which you are obviously incapable of interpreting in terms of physics.
To conclude with, I confirm that you have agreed that the circular currents which establish themselves when you switch on a magnetic field OVER AN EXISTING SUPERCONDUCTOR, ARE CAUSED BY THE INDUCED ELECTRIC FIELD. Just like Feynman has explained !
Oh yes; has the Higgs' effect been proved experimentally? Some of you guys becomes so wrapped up in your "advanced mathematics" that it does not occur to you that theoretical models ARE ONLY VALID ONCE PROVED BY EXPERIMENT!
