Condensation energy of a superconductor
= Condensation energy of a superconductor
{title2=$F_s-F_n=-a^2/(2b)$}
The <condensation energy of a superconductor> is the free-energy lowering on entering the superconducting state, with sign convention specified. For a local Landau density $a|\Delta|^2+b|\Delta|^4/2$ and $a<0$, its minimum is $-a^2/(2b)$ relative to the normal-state value. The positive <energy> required to destroy the condensate is the opposite sign.