You can find the application of the thermo field dynamics to BCS theory “the boson method” in the works of L.Leplae, F. Mancini and Umezawa.
This method is completely different to BEC method.
excuse me, BCS theory developed in Thermo field dynamics (TFD), I merely as a source the article "Derivation and application of the boson method in superconductivity" L.Leplae and all, but the method is developed for the conventional superconductivity. I want apply this method to high...