Spin-orbit scattering and pair breaking in a structurally disordered copper oxide layer.

To leading order in displacement size, the scattering of electrons in a Cu-O plane from O displacements perpendicular to that plane is due to spin-orbit coupling. This scattering is investigated with the following results: (1) As a consequence of timereversal symmetry, spin fluctuations, which can strongly enhance scattering from a spin impurity, do not enhance spin-orbit scattering; and (2) for a superconductor with a dx2−y2 gap function, pair-breaking from spin-orbit scattering can be strong, particularly in a structurally disordered phase in which locally CuO6 octahedra tilt as in the orthorhombic phase of La2CuO4, but globally the average structure is tetragonal. These results are discussed in the context of the (La,Nd)-(Sr,Ba)-Cu-O system where certain structural transitions are observed to suppress superconductivity.