Dynamic Modulation of Long Range Photon Magnon Coupling

Abstract

Evidence of non-hermitian behavior has been recently demonstrated in cavity magnonics, including the emergence of mode level attraction and exceptional points in spectroscopic measurements. This work demonstrates experimental evidence of time-domain dynamics of magnon-photon systems that are coupled through a long-range interaction (i.e. remote coupling) exhibiting level attraction mediated by an auxiliary mode. We directly observe the temporal evolution of dissipatively coupled cavity-magnon modes, where heavily damped transmission line modes mediate the interaction. Our frequency-domain measurements confirm the predicted level attraction, while time-domain ring-down measurements reveal the characteristic signatures of dissipative coupling dynamics. Our approach offers in situ tunability over the dissipative coupling strength, including complete suppression, without requiring physical modifications to the experimental setup, providing a versatile platform for exploring tunable, non-Hermitian physics.

Figures (7)

• Figure 1: (a) Experimental diagram of the remote cavity–magnon coupling system. A YIG sphere on a microstrip transmission line is coupled to a three-dimensional microwave cavity via a variable phase shifter. (b) Schematic model showing the cavity, transmission-line, and magnon modes with their associated coupling and dissipation channels.
• Figure 2: Frequency spectrum of the remote coupling system showing two distinct regimes. (a) Level attraction between cavity and magnon modes arising from dissipative coupling when $\omega_t = \omega_c$. (b) Complete magnon decoupling, $g_{mt} = 0$ and $\omega_t \neq \omega_c$. (c,d) Theoretical predictions using Eq. \ref{['eq:S11']} for panels (a) and (b), respectively. Dashed lines in all panels denote the hybridised eigenfrequencies $\omega_\pm$, calculated from Eq. \ref{['eq:analytical_eigenfreqs_final']}
• Figure 3: Time-domain response of the remote coupling system. (a) Dissipative coupling regime showing Ramsey-like interference as the system is tuned through level attraction. (b) Decoupled regime. (c,d) Theoretical calculations using Eqs. \ref{['eq:cavity']} -- \ref{['eq:transmission']} corresponding to (a) and (b), respectively.
• Figure S1: Reflection coefficient phase at frequency = 5.012GHz for different phase shifter settings $\varphi$.
• Figure S2: Reflection spectrum $|S_{11}|$ of the transmission line resonator with circle fit (inset) yielding $\gamma_t/2\pi = 50.8$ MHz, $\gamma_{\mathrm{int}}/2\pi = 9.16$ MHz, and $\gamma_{\mathrm{ext}}/2\pi = 41.7$ MHz.