Time-Varying Strong Coupling and the Induced Time Diffraction of Magnon Modes.

Time-varying media break temporal translation symmetry, enabling advanced wave manipulation. However, this phenomenon remains largely unexplored in magnonic systems due to the challenge of achieving rapid and significant changes in magnon dispersion. Here, we construct a time-varying strong coupling between two magnon modes and observe chirped Rabi-like oscillations near the pulse edges. Developing a time-resolved frequency-comb spectroscopy technique, we characterize the frequency conversion of magnon modes induced by the time-varying strong-coupling effect. Moreover, we construct time slits with adjacent time interfaces and, for the first time, demonstrate the double-slit time diffraction of magnon modes, analogous to the well-known Young's double-slit experiment. These findings rely solely on the time-varying strong coupling, independent of device reconfiguration. Our results open avenues for applications such as all-magnetic mixers or on-chip gigahertz sources.