THz-frequency magnon-phonon-polaritons in the collective strong-coupling regime

Strong coupling between light and matter occurs when the two interact such that new hybrid modes, the so-called polaritons, are formed. Here, we report on the strong coupling of both the electric and the magnetic degrees of freedom to an ultrafast terahertz (THz) frequency electromagnetic wave. In o...

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Bibliographic Details
Published in:Journal of applied physics 2019-06, Vol.125 (21)
Main Authors: Sivarajah, Prasahnt, Steinbacher, Andreas, Dastrup, Blake, Lu, Jian, Xiang, Maolin, Ren, Wei, Kamba, Stanislav, Cao, Shixun, Nelson, Keith A.
Format: Article
Language:English
Subjects:
Antiferromagnetism
Applied physics
Coupling
Electric fields
Electromagnetic radiation
Erbium
Ferroelectric materials
Ferroelectricity
Hybrid modes
Lithium niobates
Magnons
Phonons
Photonic crystals
Polaritons
Quantum electrodynamics
Spintronics
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Summary:Strong coupling between light and matter occurs when the two interact such that new hybrid modes, the so-called polaritons, are formed. Here, we report on the strong coupling of both the electric and the magnetic degrees of freedom to an ultrafast terahertz (THz) frequency electromagnetic wave. In our system, optical phonons in a slab of ferroelectric lithium niobate are strongly coupled to a THz electric field to form phonon-polaritons, which are simultaneously strongly coupled to magnons in an adjacent slab of canted antiferromagnetic erbium orthoferrite via the magnetic-field component of the same THz pulse. We juxtapose experimental results of bare slabs consisting of the two materials with a photonic crystal cavity, consisting of a two-dimensional array of air holes cut into the hybrid slab. In both cases, the strong coupling leads to the formation of new magnon-phonon-polariton modes, which we experimentally observe in the time domain as a normal-mode beating and which corresponds in the frequency domain to an avoided crossing. Our simple yet versatile waveguide platform provides a promising avenue through which to explore ultrafast THz spintronics, quantum electrodynamics, sensing, and spectroscopic applications.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5083849