Off-axial focusing of a spin-wave lens in the presence of Dzyaloshinskii-Moriya interaction

We theoretically study the effect of Dzyaloshinskii-Moriya interaction on the focusing of a spin-wave lens that is constructed by a circular interface between two magnetic films. We analytically derive the generalized Snell's law in the curved geometry and the position of the focal point which exhibits a peculiar off-axial focusing behavior. We uncover a strong dependence of the focal point on both the material parameters and the frequency of incident spin waves. Full micromagnetic simulations compare well with theoretical predictions. Our findings would be helpful to manipulate spin waves in chiral magnets and to design functional magnonic devices.