Superconducting Order Parameters in Spin Space Groups: Methodology and Application

We employ a systematic approach to construct superconducting order parameters based on the spin space group. Compared to magnetic space groups where spatial and spin rotation of elements are completely locked, the superconducting channels and the forms of basis functions in spin space groups can be different. Furthermore, we utilize the obtained basis functions to construct the Ginzburg-Landau free energy and show the possible superconducting ground states. By virtue of those results, we discuss the application of our theory to realistic systems. Our work provides a rigorous description of superconducting gap functions in the case of spin space group, and enables further study of the interplay between superconductivity and magnetism.