Magnon-magnon interaction induced by nonlinear spin wave dynamics

Abstract

We experimentally and theoretically demonstrate that nonlinear spin-wave dynamics can induce an effective resonant interaction between non-resonant magnon modes in a yttrium iron garnet disk. Under strong pumping near the ferromagnetic resonance mode, we observe a spectral splitting that emerges with increasing drive amplitude. This phenomenon is well captured by a theoretical framework based on the linearization of a magnon three-wave mixing Hamiltonian, which at high power leads to parametric Suhl instabilities. The access and control of nonlinear magnon-parametric processes enables the development of experimental platforms in an unexplored parameter regime for both classical and quantum computation protocols.

Figures (4)

• Figure 1: FMR in a driven YIG disk leading to parametric instability. (a) Schematic diagram of a magnon three-wave mixing process. A $k=0$ magnetostatic mode decays into two counter-propagating $\pm k$ modes with opposite momentum at half frequency. (b) Representation of the measured sample: YIG disk on a transmission line. (c) Measured FMR amplitude and phase response of the $k=0$ magnon mode at 28 mT. Solid lines represent a fit to the data yielding $\omega_0/2\pi=2.15$ GHz and $\gamma_{0}/2\pi=58.94$ MHz.
• Figure 2: FMR mode splitting of a strongly driven magnon mode. (a) Two-tone measurement scheme to excite and probe 3 magnon processes. A strong pump is applied at detuning $\Delta$, and a small probe is swept with detuning $\Delta_p$. (b) Map of the transmission as a function of pump power at zero detuning ($\Delta=0$). (c) Measured transmission spectrum at different drive powers for zero detuning ($\Delta=0$). The linecuts are extracted from (b) at the powers indicated with arrows, shifted by 4dB for clarity, and the data points corresponding to the strong pump and its leak image have been filtered. (d) Map of the transmission as a function of pump and probe detunings for power 10 dBm.
• Figure 3: Effective power dependent beam splitter interaction between the driven $k=0$ mode and the parametrically excited magnon pair. (a) Interaction scheme between the fluctuations of the strongly driven $k=0$ mode and the $\pm k$ mode. (b) Power dependence of the magnon mode amplitudes. The dashed line indicates the saturation power $P_{th}$. The amplitude values are normalized to the saturation amplitude of $\hat{m}_0$. (c) Power dependence of the extracted coupling $g_{\text{eff}}$ from measurement data at 30 mT, fitted with Eq. (\ref{['eq:beta_amplitude']}). The right scale indicates the correspondence with the steady state amplitude of mode $\beta$.
• Figure 4: Magnetic field dependence of the splitting. (a) Calculated dispersion relation for two magnetic fields below and above the threshold. Below the threshold, there are two pairs of available states at $\omega_0/2$ (dashed line) indicated with stars. (b) Calculated magnetic field dependence of the coupling $V_k$. The upper (lower) branch corresponds to the available state of lower (higher) $k$. Details of the calculation can be found in SI_supp. (c) Power dependence at zero pump detuning ($\Delta=0$), for magnetic fields of 40, 60, 100, and 120 mT. In the lower right corner, a schematic illustrates the dispersion relation and the corresponding position of $\omega_0/2$.