Doctoral Thesis: Hybrid Magnonics in Antiferromagnets and Cavity Spintronic Devices

Thursday, June 6
2:00 pm - 3:30 pm

36-428 Haus Room

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By: Justin T. Hou

Thesis Supervisor(s): Luqiao Liu (EECS, Thesis Supervisor), Qing Hu (EECS), William Oliver (EECS and Physics)

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  • Date: Thursday, June 6
  • Time: 2:00 pm - 3:30 pm
  • Category:
  • Location: 36-428 Haus Room
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Abstract:
Hybrid systems combine two or more subsystems to achieve control, sensing, transduction, and coherent information processing beyond the capability of each individual one. Magnons, the collective spin wave excitations in magnetically ordered materials, have recently attracted great attention for realizing hybrid systems. In my PhD works, we develop hybrid magnonic systems with reduced complexity, improved scalability, and new functionality. First, by utilizing planar microwave resonators, we realize on-chip, lithographically scalable, and Circuit Quantum Electrodynamics compatible magnon-photon hybrid systems. Strong coupling with three orders of magnitude reduction in spin number is demonstrated due to the reduced effective cavity mode volume. Moreover, the on-chip design, featuring substantial coupling strength, enables the integration of spintronic techniques to control the magnon subsystem dynamics via electrical currents. Along this line, in the second work, we theoretically propose a spin-torque-oscillator maser device, which combines a spin-torque oscillator with a resonant cavity. This device can theoretically overcome the area, power, and linewidth limitations in traditional spin-torque nano-oscillators, serving as a potential candidate for the first lithographically scalable, room-temperature maser. In the third work, we experimentally realize a tunable magnon-photon hybrid system that leverages the spin-torque effect to electrically modulate magnon dissipation. We observe distinct linewidth modulation effects in systems with different cooperativities. Finally, we realize strong magnon-magnon coupling within a single material, van der Waals antiferromagnet CrCl3, simplifying the design of magnon-magnon hybrid systems which conventionally require two magnetic materials. Our works serve as a foundation for future advancement of hybrid magnonic systems, highlighting their potential for both fundamental research and practical device applications.

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