Non-Hermitian Topological Magnonics - presented by Pr Tao Yu

Non-Hermitian Topological Magnonics

Pr Tao Yu

Pr Tao Yu
Slide at 15:08
Exceptional points Non-Hermitian Hamiltonian ==(ap-inp Wm - iK m 3400 3350 w+ = (Aw - iAk)2 + gagb (Oe) 3300 0 (mm) one eigenvector [Zhang et al., PRL 123, 237202 (2019)] Sensitiviy is much enhanced a) Fine tuning of damping and coherent coupling Away from the EPs [Harder et al., PRB 95, 214411 (2017)] At the EPs b) Competition of dissipative and coherent couplings [Yang et al., PRL 125, 147202 (2020)] c) Competition of gain and loss (PT symmetry) [Yang et al., PRL 121, 197201 (2018)] Perturbation E 2024/10/04 15:15:38
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References
  • 1.
    X. Zhang et al. (2019) Experimental Observation of an Exceptional Surface in Synthetic Dimensions with Magnon Polaritons. Physical Review Letters
  • 2.
    M. Harder et al. (2017) Topological properties of a coupled spin-photon system induced by damping. Physical Review B
  • 3.
    Y. Yang et al. (2020) Unconventional Singularity in Anti-Parity-Time Symmetric Cavity Magnonics. Physical Review Letters
  • 4.
    H. Yang et al. (2018) Antiferromagnetism Emerging in a Ferromagnet with Gain. Physical Review Letters
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Summary (AI generated)

The exceptional point is much larger than other places. An example will be shown where sensitivity is enhanced at an exceptional point. A magnetic sphere is placed on a coplanar waveguide to support traveling microwaves. The experiment measures microwave transmission by changing the external magnetic field magnitude. The external magnetic field tunes the Kittel mode of the ferromagnetic resonance of the magnetic sphere. This data process is called a probe. A microwave generator, called P, can generate microwaves to drive the magnetic sphere. This setup is a P-probe experiment. When the microwave frequency matches the ferromagnetic resonance, microwaves are absorbed by the magnetic sphere, resulting in a dip in transmission shown by the red curve. Turning on the pump reveals an anticrossing curve in the transmission spectra. The microscopic origin of this phenomenon is still unclear. The anticrossing occurs at the pump frequency, suggesting that the pump effectively drives a mode at the pump frequency, which then interacts with the parametric resonance to form the anticrossing phenomenon. The coupling strengths can be measured by this curve.