Distinguishing between s plus id and s plus is pairing symmetries in multiband superconductors through spontaneous magnetization pattern induced by a defect

The symmetry of the pairing state in iron pnictide superconductor Ba-1 xKxFe2As2 is still controversial. At optimal doping (x approximate to 0.4), it is very likely s wave, but for x = 1 there are experimental and theoretical arguments for both s wave and d wave. Depending on the choice for x = 1, intermediate s + is and s + id states have been proposed for intermediate doping 0.4 < x < 1. In both states, the time-reversal symmetry is broken and a spontaneous magnetization is allowed. In this work we study a spontaneous magnetization induced by a nonmagnetic defect in the s + is and s + id states by using a perturbation theory and numerical calculations for theGinzburg-Landau free energy functional. We showthat the angular dependence of the magnetization is distinct in these two states due to the difference in symmetry properties of the order parameters. Our results indicate a possible way to distinguish between the s + is and s + id pairing symmetries in multiband superconductors.