Proposal for a Spin-Torque-Oscillator Maser Enabled by Microwave Photon-Spin Coupling

Justin T. Hou, Pengxiang Zhang, and Luqiao Liu
Phys. Rev. Applied 16, 034034 – Published 20 September 2021

Abstract

We study a direct-current-driven maser device enabled by spin-photon coupling, where coherent magnetic self-oscillation can be realized in a large-area ferromagnetic thin film under the excitation of spin-orbit torques. We show via both micromagnetic simulation and analytical derivation that above a critical value of the coupling strength between the spin-torque oscillator and the microwave resonator, magnetic oscillation develops macroscopic phase coherence, a narrow linewidth, and becomes phase-locked with the photon mode. The threshold coupling strength for synchronizing individual spins reduces as the sample dimension increases, suggesting that the spin-torque-oscillator maser can be readily realized using large-area thin-film ferromagnets without relying on dimension confinement. Moreover, the photon mode can directly provide microwave emission, which exhibits enhanced power and a reduced linewidth with an increasing number of spins, leading to a useful approach for developing highly coherent on-chip microwave sources.

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  • Received 16 March 2021
  • Revised 12 July 2021
  • Accepted 20 August 2021

DOI:https://doi.org/10.1103/PhysRevApplied.16.034034

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Justin T. Hou, Pengxiang Zhang, and Luqiao Liu*

  • Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

  • *luqiao@mit.edu

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Vol. 16, Iss. 3 — September 2021

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