Antiferromagnetism Emerging in a Ferromagnet with Gain

Yang, Huanhuan; Wang, C.; Yu, Tianlin; Cao, Yunshan; Peng, Yan

doi:10.1103/physrevlett.121.197201

Cited by 58 publications

(55 citation statements)

References 67 publications

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“…The red circle marks the critical α for the emergence of EP3. In comparison to previous work [13], we did not note a special region where the PT symmetry is never broken. This is due to the fact that the chiral spin-spin coupling, i.e., Dzyaloshinskii-Moriya interaction, is absent in the present model.…”

Section: Trilayer Ferromagnetic Filmscontrasting

confidence: 85%

“…As first predicted in Ref. [13], for a PT -symmetry ferromagnetic bilayer, antiferromagnetism could emerge in the PT broken phase. As to the ferromagnetic trilayer, it can exhibit a FM-AFM phase transition as well.…”

Section: Trilayer Ferromagnetic Filmssupporting

confidence: 67%

“…Negative damping (gain) is the key to realize our proposal. In previous work [12,13], it has been suggested that the spin transfer torque, the parametric driving, the ferromagnetic|ferroelectric heterostructure [45], and the interaction between magnetic system and environment [46][47][48] are possible mechanisms to achieve the magnetic gain. Slavin et al analytically demonstrated that the main effect of the spin-polarized current in a "free" magnetic layer is a negative damping [49].…”

Section: Discussionmentioning

confidence: 99%

“…Hamiltonian obeying the parity-time (PT ) symmetry constitutes a special non-Hermitian system, which is invariant under combined parity P and time-reversal T operations. It has attracted a lot of attention due to both the fundamental interest in quantum theory [17][18][19] and the promising application in many fields [20][21][22], such as optics [23][24][25], tight-binding modeling [26,27], acoustics [28,29], electronics [30,31], and very recently in spintronics [12][13][14][15][16]. A PT -symmetric Hamiltonian could exhibit entirely real spectra and a spontaneous symmetry breaking accompanied by a real-to-complex spectra phase transition at the exceptional point (EP) where two or more eigenvalues and their corresponding eigenvectors coalesce simultaneously.…”

Section: Introductionmentioning

confidence: 99%

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Higher-order exceptional points in ferromagnetic trilayers

Yang

Song

et al. 2020

Phys. Rev. B

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Magnetometers with exceptional sensitivity are highly demanded in solving a variety of physical and engineering problems, such as measuring Earth's weak magnetic fields and prospecting mineral deposits and geological structures. It has been shown that the non-Hermitian degeneracy at exceptional points (EPs) can provide a new route for that purpose, because of the nonlinear response to external perturbations. One recent work [H. Yang et al., Phys. Rev. Lett. 121, 197201 (2018)] has made the first step to realize the second-order magnonic EP in ferromangetic bilayers respecting the parity-time symmetry. In this paper, we generalize the idea to higher-order cases by considering ferromagnetic trilayers consisting of a gain, a neutral, and a (balanced-)loss layer. We observe both second-and third-order magnonic EPs by tuning the interlayer coupling strength, the external magnetic field, and the gain-loss parameter. We show that the magnetic sensitivity can be enhanced by 3 orders of magnitude comparing to the conventional magnetic tunneling junction based sensors. Our results pave the way for studying high-order EPs in purely magnetic system and for designing magnetic sensors with ultrahigh sensitivity. arXiv:2002.03085v1 [cond-mat.mtrl-sci]

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Section: Trilayer Ferromagnetic Filmscontrasting

confidence: 85%

Section: Trilayer Ferromagnetic Filmssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Higher-order exceptional points in ferromagnetic trilayers

Yang

Song

et al. 2020

Phys. Rev. B

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“…The non-Hermitian degeneracy thus can significantly enhance the sensitivity [37]. Currently, PT symmetry has been investigated in a broad field of quantum mechanics [35,36,38], optics [39][40][41][42][43], acoustics [44,45], electronics [46][47][48], and very recently in spintronics [49,50] and magnonics [51][52][53][54]. However, the property of PT -symmetry and EP sensing are yet to be addressed in spin cavitronics.…”

Section: Introductionmentioning

confidence: 99%

Exceptional magnetic sensitivity of PT -symmetric cavity magnon polaritons

Cao

Peng

2019

Phys. Rev. B

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Achieving magnetometers with ultrahigh sensitivity at room temperature is an outstanding problem in physical sciences and engineering. Recently developed non-Hermitian cavity spintronics offers new possibilities. In this work, we predict an exceptional magnetic sensitivity of cavity magnon polaritons with the peculiar parity-time (PT ) symmetry. Based on the input-output formalism, we demonstrate a "Z"−shape spectrum including two side-band modes and a dark-state branch with an ultra-narrow linewidth in the exact PT phase. The spectrum evolves to a step function when the polariton touches the third-order exceptional point, accompanied by an ultrahigh sensitivity with respect to the detuning. The estimated magnetic sensitivity can approach 10 −15 T Hz −1/2 in the strong coupling region, which is two orders of magnitude higher than that of the stateof-the-art magnetoelectric sensor. We derive the condition for the noise-less sensing performance. Purcell-like effect is observed when the PT symmetry is broken. Possible experimental scheme to realize our proposal is also discussed. :1901.10685v2 [cond-mat.mes-hall] arXiv

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Parity‐Time Symmetry in Magnetic Materials and Devices

Zhang,

Xin,

Liu

2023

Adv Elect Materials

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Non‐Hermitian Hamiltonians may still possess real eigenvalues in case of the existence of parity‐time (PT) symmetry. Exceptional points (EPs) occur at the phase transition from real to complex eigenvalues due to PT‐symmetry breaking in the parameter space. Magnonic devices use magnons to carry, transport, and process information, which have the advantages of low energy dissipation, wave‐based computing, and nonlinear data processing. The combination of PT‐symmetry and magnonics may lead to novel physics as well as unprecedented functional device applications. Recently, the research of PT‐symmetry in magnetism has developed rapidly. In this review, the theoretical predictions as well as experimental findings of PT‐symmetry in magnetism are summarized. First, a brief introduction to PT symmetry, EPs, and anti‐PT symmetry is presented. Second, the theoretical and experimental progress of magnonic PT symmetry are summarized. Third, the theoretical predictions of higher‐order EPs and anti‐PT symmetry in magnonic systems are given. Finally, the study concludes by discussing the future challenges and research prospects in magnonic PT‐symmetry, and proposals for experimental observations of magnonic higher‐order EPs and anti‐PT symmetry are suggested.

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Antiferromagnetism Emerging in a Ferromagnet with Gain

Cited by 58 publications

References 67 publications

Higher-order exceptional points in ferromagnetic trilayers

Higher-order exceptional points in ferromagnetic trilayers

Exceptional magnetic sensitivity of PT -symmetric cavity magnon polaritons

Parity‐Time Symmetry in Magnetic Materials and Devices

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