On-Chip Magnon-Photon Hybrid System Using YSGG/YIG Film with a Superconducting Circuit in Flip-Chip Architecture

Hybrid quantum systems offer potential not only for storing and converting quantum information but also for observing quantum phenomena of quasiparticles such as phonons and magnons [1, 2]. In the emerging field of hybrid magnonics, achieving strong magnon-photon coupling requires coupling low-dissipation magnetic materials like Yttrium Iron Garnet (YIG) to superconducting resonators [3]. However, conventional YIG systems grown on Gadolinium Gallium Garnet (GGG) substrate face significant challenges at low temperatures below 100 K, where the paramagnetism of the GGG causes a substantial increase in the magnon dissipation rate [4]. Here, we demonstrate an on-chip strong magnon-photon hybrid system using 100 nm YIG film grown on Yttrium Scandium Gallium Garnet (YSGG) substrate and NbN superconducting resonator. Using a flip-chip technique, a 2.5 mm x 2.5 mm piece of the YSGG/YIG film was integrated to a coplanar waveguide superconducting resonator made from a 200 nm NbN film on a Si substrate. Below 100 K, the Gilbert damping constant of magnon in the YSGG/YIG film decreases with decreasing temperature, reaching approximately low-10^-4 below 10 K. By measuring the microwave spectrum as a function of the applied magnetic field, we observe a clear band anti-crossing, indicating strong magnon-photon coupling with a coupling strength of g/2π = 60 MHz at a resonance frequency of 3 GHz. Our demonstration of the successful integration of superconducting circuits with low-dissipation magnetic films opens up new possibilities to involve the unique properties of propagating magnons, such as parametric pumping or magnon Bose-Einstein condensation, which were previously unattainable with YIG spheres, paving the way for novel approaches to quantum magnonics.

[1] K. J. Satzinger et al., Nature 563, 661-665 (2018)

[2] D. Lachance-Quirion et al., Science 367, 425-428 (2020)

[3] Y. Li et al., Physical Review Letters 128, 047701 (2022).

[4] S. Guo et al., Nano Letters 23, 5055-5060 (2023)