# Gibbs Free Energy in Superconductors

## Main Question or Discussion Point

When reading some material concerning Ginzburg-Landau theory of superconductors, I got the following sentence:

The appropriate thermodynamic potential for describing a superconductor in an applied magnetic field is the Gibbs free energy $G$ (natural variable $H$) and not the Helmholtz free energy $F$ (natural variable $B$).

I don't understand the sentence. In gas, Gibbs free energy is minimal in constant temperature and pressure. Does this sentence mean that in superconductors Gibbs free energy is minimal in constant $T$ and $H$? I can't make sense out of it.

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DrDu
L&L discuss quite extensively their peferred thermodynamic variables in the case of magnetic fields in previous chapters.

L&L discuss quite extensively their peferred thermodynamic variables in the case of magnetic fields in previous chapters.
You mean Landau and Lifshitz‘s textbook?

DrDu