Microwave Transmission Theory for On-Chip Ultrastrong-Coupled Magnon-Polariton in Dynamical Inductors

Abstract

  We present a microwave transmission theory for recently proposed ultrastrong-coupled magnon-polariton (MP) in dynamical inductors which consist of a coil involving a magnetic insulator. Combining with the RLC-circuit and Landau-Lifshitz-Gilbert equations, we formulate the electric impedance of MP as a coupled oscillator under the corresponding principle. Based on the transmission (ABCD or F) matrix approach, we further calculate S₂₁ being a scattering parameter for the microwave transmission measurement passing through an RLC-circuit with the dynamical inductor. By tunning the size of the dynamical inductor, we theoretically demonstrate an on-chip ultrastrong-coupled MP at room temperature, which reaches a coupling ratio about 0.55 and cooperativity about 2×10⁵ with material parameters of Y₃Fe₅O₁₂. This work paves the way for quasi-two-dimensional circuit/wave-guide based magnonics for quantum information technology.