Two component solution for an alternative order parameter in HTSC

In an early study the BCS wave function was generalized to include the motion of the center-of-mass of Cooper pairs. An alternative order parameter can be defined on the basis of this motion. In later work, when in copper oxides Bloch orbitals replaced free electrons, nodes were found in the vector space of the Fourier representation of the order parameter. Here that Fourier representation has suggested that the parameter consists of two components, a long wave lengths part which does not contain nodes, a short wave length part which does. The former component is real, and applies deep inside the superconductor, the latter, which is imaginary, in the boundary region. Further, the imaginary component has odd symmetry about the nodal axis. There results an addition of about 0.93π to the relative phase of two adjacent sides of a square superconductor cut along appropriate crystal axis, and embedded in a normal metal.