BCS Theory explained

Updated website at: http://sciencehsc.com.au 


The BCS theory of superconductivity explains that lattice distortions at below critical temperatures lead to the formation of Cooper pairs. Bardeen, Cooper and Schrieffer modelled this theory to successfully explain Type I superconductors.

Type I superconductors are metals which exhibit superconducting properties at below their critical temperature. All of which are below 30K. Note that the BCS theory cannot explain superconductivity in Type II superconductors (made from ceramics and have much higher critical temperatures) as its structure is more complicated.

Examples of Type I superconductors and their critical temperatures:
Zinc – 0.85K
Mercury – 4.15K
Tin – 7.72

As the Type I superconductor is cooled to below critical temperature, the lattice vibrations are minimised. An electron passing through the structure will attract the positive lattice, thus distorting the structure. This distortion releases a phonon (a packet of vibrational energy) and creates a net positive area. Another electron is attracted to this area, absorbing the phonon providing it sufficient energy to overcome electrostatic repulsion and joins with the initial electron, forming a Cooper pair. The Cooper pair acts as one particle and can move through the lattice unimpeded, thus there is zero electrical resistance.

If you have any questions feel free to ask in the comments.


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