New Findings of the Electromagnetic Response in

Based on the Ginzburg-Landau theory, two theoretical findings in the electromag-netic response of superconductors are described. First, we derive the most general linear response theory and then apply it to the charged super fluid regime, where the magnetic fluctuation is relevant. In particular, we show that a novel effect arises, in which the divergence of the conductivity tensor is suppressed by the diamagnetic susceptibilities. Secondly, we show that because of the approximated fourfold symmetry of the crystal lattice in high T, cuprates, a non-vanishing Hall current can arise near HQ. This Hall current is non-linear and can become large to be observed if the applied electric field is large enough. PACS. 74.20.De ~ ~ Phenomenological theories. PACS. 74.25.F ~ Transport properties