Observation of magnon cross-Kerr effect in cavity magnonics

Abstract

When there is a certain amount of field inhomogeneity, the biased ferrimagnetic crystal will exhibit the higher-order magnetostatic (HMS) mode in addition to the uniform-precession Kittel mode. In cavity magnonics, we show both experimentally and theoretically the cross-Kerr-type interaction between the Kittel mode and HMS mode. When the Kittel mode is driven to generate a certain number of excitations, the HMS mode displays a corresponding frequency shift, and vice versa. The cross-Kerr effect is caused by an exchange interaction between these two spin-wave modes. Utilizing the cross-Kerr effect, we realize and integrate a multi-mode cavity magnonic system with only one yttrium iron garnet (YIG) sphere. Our results will bring new methods to magnetization dynamics studies and pave a way for novel cavity magnonic devices by including the magnetostatic mode-mode interaction as an operational degree of freedom.

Steady entangled-state generation via cross-Kerr effect in a ferrimagnetic crystal

“…1(a). The spin-wave mode interacts with the cavity photon mode via a magnetic dipole-dipole interaction, while the HMS mode couples to the Kittel mode via mode overlap [67,71,72]. The Hamiltonian of the whole system reads , so derivations of the latter ones will not be repeated hereafter.…”

“…Cross-Kerr interactions, as a type of nonlinear interaction between fields and waves, have been observed in a variety of systems, including superconducting circuits [59][60][61], atoms [62][63][64], and ions [65], among others. Recently, the cross-Kerr interaction between the higher-order magnetostatic (HMS) mode and the spin uniform precession mode (referred to as the Kittel mode [66]) in cavity magnonics was experimentally observed [67]. When only one mode is driven, the two spin-wave modes simultaneously undergo nonlinear frequency shift, proving that self-and cross-Kerr effects are simultaneously excited.…”

Unveiling Pump induced Magnon Mode via its Strong Interaction with Walker Modes

“…But via its interaction with Walker modes, we can indirectly detect it. Here we mainly consider the Zeeman interaction between its net magnetization and the demagnetization field by the Walker mode M w (r), or vice versa, which we model as [36,47], where η represents an effective demagnetization factor O(1) and V is the volume of the YIG sphere [42]. Note that we have disregarded many complications such as the spin textures of the PIM and Walker mode in this effective model, but focus only on the key features that help to understand our nontrivial observations.…”

“…We use â † (â) and b † ( b) to represent, respectively, the creation (annihilation) operators of the Walker mode and the PIM. Expanding M w and M p in terms of them, we can derive the interaction Hamiltonian of the two modes [36,42]. Further considering the pump and probe drivings, the Hamiltonian of our system reads…”

“…The PIM can be continuously tuned by the pump over a wide frequency range and maintain a narrow linewidth (∼ 500 kHz). When the anticrossing appears, the radiation spectrum of our system reads out multi-peaks with equal frequency intervals that demonstrates the frequency comb [37][38][39][40][41] functionality, produced by mixing the pump and probe signals via the cross-Kerr nonlinearity [42][43][44]. Anti-crossing of Walker modes in a waveguide.-The CPW, fabricated on a 22×50 mm 2 RO4350B board, has a standard impedance of 50 Ω.…”