Theory of magnon polaritons in quantum Ising materials
Abstract
We present a theory of magnon polaritons in quantum Ising materials, and develop a formalism describing the coupling between light and matter in an Ising system that is tuned through its quantum critical point. The theory is applied to Ising materials having multilevel single-site Hamiltonians, in which multiple magnon modes are present, such as the insulating Ising magnet LiHoF₄. We find that the magnon-photon coupling strengths may be tuned by the applied transverse field, with the coupling between the soft mode present in the quantum Ising material and a photonic resonator mode diverging at the quantum critical point of the material. A fixed system of spins will not exhibit the diamagnetic response expected when light is coupled to mobile spins or atoms. Without the diamagnetic response, one expects a divergent magnon-photon coupling strength to lead to a superradiant quantum phase transition. However, this neglects the effects of damping and decoherence present in any real system. We show that damping and decoherence may block the superradiant quantum phase transition, and lead to weak coupling between the soft magnon mode and the resonator mode. The results of the theory are applied to experimental data on the model system LiHoF₄ in a microwave resonator.
Additional Information
© 2022 American Physical Society. The authors would like to thank Yikai Yang and Philip Stamp for helpful discussions. Experimental work at the California Institute of Technology was supported by U.S. Department of Energy Basic Energy Sciences Grant No. DE-SC0014866.Attached Files
Published - PhysRevA.106.043716.pdf
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Additional details
- Eprint ID
- 122248
- Resolver ID
- CaltechAUTHORS:20230712-104705000.1
- DE-SC0014866
- Department of Energy (DOE)
- Created
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2023-08-11Created from EPrint's datestamp field
- Updated
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2023-08-14Created from EPrint's last_modified field