Non-Hermitian Topological Magnonics

The ferromagnet has been replaced by an insulator, creating a structure with two normal metals separated by an insulator, resembling a plane-parallel capacitor. The dynamics of the electromagnetic field in this structure are now being analyzed. The electric field can be either in-plane or out-of-plane. Let's first consider the out-of-plane component. The out-of-plane electric field (E_z) causes charge accumulation on the upper and lower normal metal layers, generating a voltage across the insulator. This charge accumulation results in the electric field only existing in the insulator layer, vanishing in the normal metal. As for the in-plane magnetic field, it is continuous at the interface, allowing it to penetrate into the normal metals and drive current within them. The blue curve represents the distribution of the electric field. The total current in one normal layer can be found using the equation: (I = ∫ B \cdot dl), connecting the total current to the magnetic field. The electric field can induce a voltage across the insulator and also generate total current in the normal metal.