Magnon dark mode in a strong driving microwave cavity

Abstract

Inspired by the new discovery that the nonlinear dynamics of the cavity magnon polaritons have been observed with a small yttrium iron garnet (YIG) sphere (which introduces a nonlinear Kerr effect) placed into a microwave cavity, we theoretically study the nonlinear behaviors of the magnon dark mode without the magnon Kerr effect by inserting two YIG spheres into a microwave cavity under the strong driving field. The resulting bistability features of the magnon dark mode are sensitive to the frequency detuning between two YIGs and the magnetic field. Especially, when two YIGs have a finite frequency detuning, the magnon dark mode at the cavity resonance frequency does not display bistability. Our research not only sheds light on the nonlinear effect of the magnon dark mode in a strong driving field but also provides a theoretical basis for the application in information storage and novel spintronics.