How does or does not BCS theory explain Meissner's Effect?

calvinjhfeng

I am reading through BCS's original paper from 1957 on PhysReview. It is very difficult for me to actually understand every word it says, I am unfamiliar with most terminology the paper mentioned. However I know most of the very basic mechanism of this theory. I understand how superconductivity came to form but I just still find it unclear with the Meissner's effect.

I am not sure if I have misread it or it just does not explain Meissner's effect explicitly.

I think what B. C. S. are arguing is that Meissner's effect is a consequence of energy gap, and from my understanding energy gap is the energy required to break Cooper's pairs.
So why is Meissner's effect a consequence of energy gap? or somehow related to it?

Does it give lower energy to the system when magnetic field isn't penetrated through the system?

Thank you for your time.

shawl

That was one of significant paper exciting everyone in the field of superconductor.

In history of superconductor,"two current" model (Normal current and superconducting one) was first proposed by London brothers, explaining such zero-resistance conducting phenomenon. Company with Electromagnetism theory, it could also explain Meissner's effect.

However, people had no idea about how the superconducting current was generated. A possible process was considered to be electron-phonon coupling. Bardeen et al put forward the idea and suceeded to explain the formation of superconducting current in Type-I superconductor.

DrDu

That's kind of a tricky question. BCS theory only describes correctly the ground state of a system which does not interact with the electromagnetic field, but fails to describe coupling to the electromagentic field. This immediately spurred attempts to explain the Meissner Ochsenfeld effect. Nevertheless this took several years and lead to further important theoretical insights i.e. spontaneous symmetry breaking, the Goldstone theorem and the Higgs mechanism.
An nice introduction is the Nobel lecture of Nambu:
http://www.nobelprize.org/nobel_priz...bu_lecture.pdf

shawl

In my knowledge, BCS did make a deep prediction in the situation of the weak electromagnetic field of type-I superconductor. Please refer to the book <theory of superconductivity> written by J. R. Schrieffer, who is the third person in BCS theory.

Surely spontaneous symmetry breaking and other theories are important and have been put forward in the frontier of this field. But note that they are prepared for type-II superconductor.

DrDu

Very interesting is also the article by Weinberg:
Superconductivity for Particular Theorists
Steven Weinberg
Prog. Theor. Phys. Suppl. 86 (1986) 43

ZapperZ

OK, I'm not understanding the issue being discussed here in this thread. I think there's something that has been seriously missed.

1. The London equation describes the Meissner effect.

2. Wouldn't it be sufficient to show that the BCS theory can derive the London equation? I thought this was done in the BCS paper? If not, Tinkham shows this rather clearly in his classic text.

So I don't get it. What did I miss here?

Zz.