pith. sign in

arxiv: 2508.04298 · v1 · submitted 2025-08-06 · 🪐 quant-ph

Coupling phase enabled level transitions in pseudo-Hermitian magnon-polariton systems

Pith reviewed 2026-05-19 00:42 UTC · model grok-4.3

classification 🪐 quant-ph
keywords pseudo-Hermitian systemsmagnon-polaritonexceptional pointslevel attractionlevel repulsionnon-Hermitian physicsspintronicscavity magnonics
0
0 comments X

The pith

In pseudo-Hermitian magnon-polariton systems, symmetry breaking is linked to transitions in coupling modes.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper proposes a model of two magnon modes and two cavity modes interacting through phase-dependent coupling under pseudo-Hermitian conditions. It maps out how the energy levels behave as non-Hermiticity and the coupling phase change, showing exceptional points at symmetry breaking. The work connects these breaks to switches between level attraction and repulsion regimes. A reader might care because it suggests ways to manage damping in quantum hybrid systems by using balanced gain and loss, potentially improving control in spintronic applications.

Core claim

We propose a pseudo-Hermitian model with two magnon and two cavity modes coupled via phase-dependent interaction. Linking the energy spectrum to phase transitions, we observe exceptional points when pseudo-Hermitian symmetry breaks. Level attraction corresponds to four phase transitions and appears as a double Z-shaped energy spectrum, while level repulsion corresponds to two phase transitions with a gap depending on the coupling phase. In the phase diagram defined by non-Hermiticity and coupling phase, pseudo-Hermitian symmetry breaking is intrinsically linked to coupling mode transitions.

What carries the argument

The phase diagram in non-Hermiticity and coupling phase space that reveals the intrinsic link between pseudo-Hermitian symmetry breaking and coupling mode transitions.

If this is right

  • Exceptional points emerge precisely when the pseudo-Hermitian symmetry breaks.
  • Level attraction manifests as a double Z-shaped spectrum tied to four phase transitions.
  • Level repulsion shows a phase-dependent gap across two transitions.
  • This correspondence enables new strategies for controlling hybrid quantum states in spintronic systems.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Similar phase-dependent mechanisms could be explored in other non-Hermitian hybrid systems to achieve tunable level structures.
  • Experimental setups with adjustable gain in magnon-cavity systems might test and utilize these transitions for quantum sensing.
  • The model suggests potential for designing devices that switch between attractive and repulsive regimes via phase control.

Load-bearing premise

Tunable external gain can be introduced at the macroscopic scale to maintain gain-loss balance in the magnon and cavity modes while preserving the pseudo-Hermitian description.

What would settle it

An experiment that varies the coupling phase and non-Hermiticity parameter and finds no correspondence between symmetry breaking and the expected level transitions or exceptional points would disprove the claimed link.

Figures

Figures reproduced from arXiv: 2508.04298 by Huang Xin, Lin Shirong, Liu Jingyu.

Figure 1
Figure 1. Figure 1: (a) Coupling model diagram. (b) Schematic [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: Evolution of the eigenfrequency ω/g with the magnon frequency ωm/g. The parameters γ/g and θ are set as follows: (a) 0.5, 0◦ ; (b) P, 0◦ ; (c) 1.6, 0◦ . The panels (d), (e), and (f) show the S21 spectra corresponding to panels (a), (b), and (c), respectively. The normalized S21 as a function of ω/g for different values of detuning ∆ as shown in panels (g), (h), and (i). The values of ωc,1/g = 24, ωc,2/g = … view at source ↗
Figure 4
Figure 4. Figure 4: (a) The system phase diagram at θ = 45◦ . (b) The system phase diagram at θ = 90◦ . The strong resonance region refers to the area near ωm = ωc, with the resonance center being at ωm = ωc. We then analyze the corresponding energy spec￾trum. For [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
Figure 2
Figure 2. Figure 2: Next, we analyze the phase transition of the [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: The energy spectrum of the system shows the evolution of the eigenfrequency [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: The distribution of phase transitions and [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 8
Figure 8. Figure 8: (a) shows the pseudo-Hermitian phase dia￾gram determined by the coupling phase and the non￾Hermiticity. The green region represents the real do￾main, where selecting any point within this area en￾sures that all eigenvalues are real. The boundary of this phase diagram is also marked by EPs. Next, we calculate the pseudo-Hermitian energy band struc￾ture at points (θ, γ/g) in [PITH_FULL_IMAGE:figures/full_fi… view at source ↗
read the original abstract

While cavity-magnon hybridization offers intriguing physics, its practical implementation is hindered by intrinsic damping in both cavity and magnon modes, leading to short coherence times and constrained applications. Recently, with the emergence of tunable external gain at the macroscopic scale, the research focus has shifted from purely lossy systems to gain-loss balanced non-Hermitian systems. Here, we propose a pseudo-Hermitian model with two magnon and two cavity modes coupled via phase-dependent interaction. We link the energy spectrum to phase transitions, observing exceptional points when pseudo-Hermitian symmetry breaks. We also observed level attraction and level repulsion. The former corresponds to four phase transitions and manifests as a double Z-shaped energy spectrum, the latter corresponds to two phase transitions, with the repulsive gap depending on the coupling phase. In the phase diagram defined by non-Hermiticity and coupling phase, we reveal a distinctive correspondence: pseudo-Hermitian symmetry breaking is intrinsically linked to coupling mode transitions, enabling new strategies for controlling hybrid quantum states in spintronic systems.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript proposes a pseudo-Hermitian model with two magnon modes and two cavity modes coupled by a phase-dependent interaction. The authors derive the energy spectra, locate exceptional points associated with the breaking of pseudo-Hermitian symmetry, and present a phase diagram in the plane of non-Hermiticity strength and coupling phase. They report level attraction as a double Z-shaped spectrum linked to four phase transitions and level repulsion whose gap depends on the coupling phase and corresponds to two transitions. The central result is an observed correspondence between pseudo-Hermitian symmetry breaking and coupling-mode transitions.

Significance. If the derived correspondence holds, the work supplies a concrete theoretical link between symmetry breaking and mode transitions that could be exploited to control hybrid magnon-polariton states by tuning the coupling phase. The explicit construction of the metric operator and the numerical phase diagram constitute reproducible elements that strengthen the internal consistency of the mapping.

major comments (1)
  1. [§4] §4, phase-diagram construction: the reported one-to-one linkage between symmetry-breaking points and mode-transition lines follows directly from the eigenvalue analysis of the non-Hermitian Hamiltonian; the manuscript should state explicitly whether this correspondence is an independent physical prediction or a direct consequence of the chosen phase-dependent coupling term.
minor comments (2)
  1. [Figure 3] Figure 3: the color bar for the phase diagram lacks explicit labels for the symmetry-breaking and mode-transition regions, complicating direct visual comparison with the text description.
  2. [Eq. (8)] Eq. (8): the definition of the metric operator is given without a brief derivation step; adding one sentence would improve traceability from the Hamiltonian to the pseudo-Hermitian condition.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive evaluation of our manuscript and for the constructive comment regarding the phase-diagram construction. We address the point raised below and have made revisions to improve clarity.

read point-by-point responses
  1. Referee: §4, phase-diagram construction: the reported one-to-one linkage between symmetry-breaking points and mode-transition lines follows directly from the eigenvalue analysis of the non-Hermitian Hamiltonian; the manuscript should state explicitly whether this correspondence is an independent physical prediction or a direct consequence of the chosen phase-dependent coupling term.

    Authors: We agree that the reported one-to-one correspondence between pseudo-Hermitian symmetry-breaking points and coupling-mode transition lines follows directly from the eigenvalue analysis of the non-Hermitian Hamiltonian. This linkage is not presented as an independent physical prediction but arises as a direct consequence of the phase-dependent coupling term in our four-mode model. The phase dependence specifically enables the double Z-shaped spectrum associated with four transitions (level attraction) and the phase-tunable gap with two transitions (level repulsion), both tied to symmetry breaking. In the revised Section 4, we have added explicit language clarifying that the correspondence is a feature of the chosen interaction form and the resulting spectral structure, while noting its utility for controlling hybrid magnon-polariton states. This revision does not change the central results but addresses the requested distinction. revision: yes

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained

full rationale

The paper defines a pseudo-Hermitian Hamiltonian with explicit phase-dependent coupling between magnon and cavity modes, then computes the energy spectra, exceptional points, level attraction/repulsion features, and the phase diagram directly from the eigenvalue problem of that Hamiltonian. The reported correspondence between pseudo-Hermitian symmetry breaking and coupling-mode transitions is an observed outcome of varying the non-Hermiticity strength and coupling phase within the model; it does not reduce to a fitted parameter renamed as prediction, a self-definitional loop, or a load-bearing self-citation. The derivation remains independent of external benchmarks and contains no quoted step that equates an output to its input by construction.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on the assumption that a phase-dependent interaction term can be engineered while maintaining pseudo-Hermiticity; no new particles or forces are postulated, but the external gain mechanism is treated as an available resource.

free parameters (1)
  • coupling phase
    The phase angle in the interaction Hamiltonian is introduced as a tunable parameter that directly controls the observed attraction/repulsion behavior.
axioms (1)
  • domain assumption The four-mode system admits a pseudo-Hermitian description once external gain balances intrinsic losses.
    Invoked to justify the existence of exceptional points and the phase diagram.

pith-pipeline@v0.9.0 · 5707 in / 1302 out tokens · 53656 ms · 2026-05-19T00:42:08.235138+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

50 extracted references · 50 canonical work pages

  1. [1]

    Huebl H, Zollitsch C W, Lotze J, Hocke F, Greifenstein M, Marx A, Gross R and Goennenwein S T B 2013 Phys. Rev. Lett. 111 127003 7

  2. [2]

    Zhang X, Zou C L, Jiang L and Tang H X 2014 Phys. Rev. Lett. 113 156401

  3. [3]

    Zhang X, Zou C L, Zhu N, Marquardt F, Jiang L and Tang H X 2015 Nat. Commun. 6 8914

  4. [4]

    Bai L, Harder M, Hyde P, Zhang Z, Hu C M, Chen Y P and Xiao J Q 2017 Phys. Rev. Lett. 118 217201

  5. [5]

    Zhang D, Luo X Q, Wang Y P, Li T F and You J Q 2017 Nat. Commun. 8 1368

  6. [6]

    Wang Y P, Zhang G Q, Zhang D, Li T F, Hu C M and You J Q 2018 Phys. Rev. Lett. 120 057202

  7. [7]

    Lin S, Nie Z, Yan W, Liang Y, Lin H, Zhao Q and Jia B 2019 Nanophotonics 8 2177-2188

  8. [8]

    2024 Adv

    Guo Z, Wang J, Malinowski G, Zhang B, Zhang W, Wang H, Lyu C, Peng Y, Vallobra P, Xu Y, et al. 2024 Adv. Mater. 36 2311643

  9. [9]

    Zhou C-L, Wu X-H, Zhang Y, Yi H-L, Antezza M 2021 Phys. Rev. B 103 155404

  10. [10]

    Wu H, Huang L, Fang C, Yang B S, Wan C H, Yu G Q, Feng J F, Wei H X, Han X F 2018 Phys. Rev. Lett. 120 097205

  11. [11]

    Han X, Wu H, Zhang T 2024 Appl. Phys. Lett. 125 2

  12. [12]

    Wu H, Wan C H, Zhang X, Yuan Z H, Zhang Q T, Qin J Y, Wei H X, Han X F and Zhang S 2016 Phys. Rev. B 93 060403

  13. [13]

    Guo Y, Zhang X, Huang Z, Chen J, Luo Z, Zhang J, Li J, Zhang Z, Zhao J, Han X and others 2024 npj Spintronics 2 36

  14. [14]

    Jiang Z, Lim J, Li Y, Pfaff W, Lo T H, Qian J, Schleife A, Zuo J M, Novosad V and Hoffmann A 2023 Appl. Phys. Lett. 123 13

  15. [15]

    Agarwal G S 1984 Phys. Rev. Lett. 53 1732

  16. [16]

    10 2786-2793

    Liu Z X and Li Y Q 2022 Photonics Res. 10 2786-2793

  17. [17]

    Xie H, He L W, Shang X, Lin G W and Lin X M 2022 Phys. Rev. A 106 053707

  18. [18]

    Bhoi B, Cliff T, Maksymov I S, Kostylev M, Aiyar R P R C, Venkataramani N, Prasad S V G V A and Stamps R L 2014 J. Appl. Phys. 116 24

  19. [19]

    Tabuchi Y, Ishino S, Ishikawa T, Yamazaki R, Usami K and Nakamura Y 2014 Phys. Rev. Lett. 113 083603

  20. [20]

    Zhang D, Wang X M, Li T F, Luo X Q, Wu W, Nori F and You J Q 2015 NPJ Quantum Inf. 1 1-6

  21. [21]

    Yan P, Wang X S and Wang X R 2011 Phys. Rev. Lett. 107 177207

  22. [22]

    Nair J M P, Zhang Z, Scully M O and Agarwal G S 2020 Phys. Rev. B 102 104415

  23. [23]

    Yao B, Gui Y S, Rao J W, Kaur S, Chen X S, Lu W, Xiao Y, Guo H, Marzlin K-P and Hu C-M 2017 Nat. Commun. 8 1437

  24. [24]

    Lachance-Quirion D, Tabuchi Y, Ishino S, Noguchi A, Ishikawa T, Yamazaki R, Nakamura Y 2017 Sci. Adv. 3 e1603150

  25. [25]

    Bai L, Harder M, Chen Y P, Fan X, Xiao J Q and Hu C-M 2015 Phys. Rev. Lett. 114 227201

  26. [26]

    Grigoryan V L, Shen K and Xia K 2018 Phys. Rev. B 98 024406

  27. [27]

    Harder M, Yang Y, Yao B M, Yu C H, Rao J W, Gui Y S, Stamps R L and Hu C-M 2018 Phys. Rev. Lett. 121 137203

  28. [28]

    Yuan H Y, Liu Q, Xia K, Yuan Z and Wang X R 2019 Europhys. Lett. 126 67006

  29. [29]

    Wang Y-P, Rao J W, Yang Y, Xu P-C, Gui Y S, Yao B M, You J Q and Hu C-M 2019 Phys. Rev. Lett. 123 127202

  30. [30]

    Zhang C, Jia C L, Shi Y Z, Jiang C J, Xue D S, Ong C K and Chai G 2021 Phys. Rev. B 103 184427

  31. [31]

    Yuan H Y, Yan P, Zheng S, He Q Y, Xia K and Yung M-H 2020 Phys. Rev. Lett. 124 053602

  32. [32]

    Lin S, Liang Y, Zhang J C, Chen M K and Tsai D P 2023 Appl. Phys. Lett. 123 22

  33. [33]

    Zhang G-Q and You J Q 2019 Phys. Rev. B 99 054404

  34. [34]

    Mostafazadeh A 2002 J. Math. Phys. 43 205–214

  35. [35]

    Vogt K, Fradin F Y, Pearson J E, Sebastian T, Bader S D, Hillebrands B, Hoffmann A and Schultheiss H 2014 Nat. Commun. 5 3727

  36. [36]

    Dark Univ

    Flower G, Bourhill J, Goryachev M and Tobar M E 2019 Phys. Dark Univ. 25 100306

  37. [37]

    2021 Appl

    Baity P G, Bozhko D A, Macˆ edo R, Smith W, Holland R C, Danilin S, Seferai V, Barbosa J, Peroor R R, Goldman S et al. 2021 Appl. Phys. Lett. 119 3

  38. [38]

    Liu H, Sun D, Zhang C, Groesbeck M, McLaughlin R and Vardeny Z V 2019 Sci. Adv. 5 eaax9144

  39. [39]

    Wang C and Wang X R 2020 Phys. Rev. B 101 165114

  40. [40]

    Wang C and Wang X R 2023 Phys. Rev. B 107 024202

  41. [41]

    Wang C and Wang X R 2022 Phys. Rev. B 106 045142

  42. [42]

    Zhang X, Liu C, Zhu Z, Zhang Y 2024 Phys. Rev. B 109 184426

  43. [43]

    Holstein T and Primakoff H 1940 Phys. Rev. 58 1098

  44. [44]

    Cao Y and Yan P 2019 Phys. Rev. B 99 214415

  45. [45]

    Shen X, Wang F, Li Z and Wu Z 2019 Phys. Rev. A 100 062514

  46. [46]

    Soykal ¨O O, Flatt´ e M E 2010Phys. Rev. Lett. 104 077202

  47. [47]

    Lin S, Wang L, Yuan L and Chen X 2022 Phys. Rev. Appl. 17 064029

  48. [48]

    Gardin A, Bourhill J, Vlaminck V, Person C, Fumeaux C, Castel V and Tettamanzi G C 2023 Phys. Rev. Appl. 19 054069

  49. [49]

    Gardin A, Bourcin G, Bourhill J, Vlaminck V, Person C, Fumeaux C, Tettamanzi G C and Castel V 2024 Phys. Rev. Appl. 21 064033

  50. [50]

    Gardiner C W and Collett M J 1985 Phys. Rev. A 31 3761 8