Composite operators for BCS superconductor
Bonca J., Balatsky A.V.
The, new fo^m of the composite operator generalizing the Cooper pairs for a BCS superconductor is introduced. The approach is similar to the derivation of the composite operator of the odd frequency superconductors. The examples of the dxa_y2, dxy and p-wave composite operators for a 2D t — J model are given.