Optimizing the Lumped Element Resonator via changing the total capacitance and the coplanar waveguide distance for effective magnon-photon coupling*

Controllable superconducting quantum circuits with strong coupling strength is a key ingredient in the study of magnon-photon coupling in hybrid magnonic systems. The circuit's impedance is a crucial factor for optimizing the magnon-photon coupling as it strongly affects the current-flow pattern. Here, we explore the low-impedance lumped element resonator which is capacitively side-coupled to the signal line of a coplanar waveguide, by altering key parameters that were characterized with a triple-axis vector magnet at 1.5 K. The resonance frequencies are found to be inversely proportional to the circuit's total capacitance. The coupling strength is mostly affected by the distance between them. We identified a critical coupling strength, which suggests an optimal quality-factor along with a minimum insertion loss. Our studies reveal an alternative route to increase the susceptibility of magnon-photon coupling.