•P.W. Anderson Phy. Rev. 130 (1963) 439
•S. Weinberg, - “Quantum
Theory of Fields”
•Tilley & Tilley – “Superfluidty and Superconductivity”
T<Tc ~ D
Superconducting state
Order parameter field
-“Macroscopic wave function”
Superconducting condensate
fraction: