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What is the Difference Between BCS Theory and Ginzburg-Landau Theory?

I have been studying Superconductivity and I know that Both of the theories (BCS Theory and Ginzburg-Landau Theory) can be used to explain Superconductivity - but how do they differ?

'BCS Theory' is also known as 'Bardeen-Cooper-Schrieffer Theory'.

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    $\begingroup$ Ginzburg-Landau theory is the low energy effective theory that describes the macroscopic phenomenology of superconductivity. But it does not say how from microscopic interactions the SC state came to be. This is what BCS theory does for so-called conventional SC's. So the difference is macroscopic vs microscopic. You can essentially derive Ginzburg-Landau theory from BCS theory. However, the Ginzburg-Landau theory is still valid for High T_C SC's. But we don't know a general microscopic theory for those (BCS dosen't work there). $\endgroup$
    – Heidar
    Commented Dec 1, 2014 at 22:52

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The short answer is that BCS theory is derived bottom-up from quantum mechanics (you assume that there is some local attractive interaction between electrons, and perform a mean field approximation), while the older Ginzburg-Landau theory is derived top-down from thermodynamics (you assume that superconductivity can be described by some order parameter, and perform a series expansion of the Helmholtz free energy in the order parameter near the critical point).

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