Ultrastrong magnon–magnon coupling dominated by antiresonant interactions

Takuma Makihara, Kenji Hayashida, G. Timothy Noe, Xinwei Li, Nicolas Marquez Peraca, Xiaoxuan Ma, Zuanming Jin, Wei Ren, Guohong Ma, Ikufumi Katayama, Jun Takeda, Hiroyuki Nojiri, Dmitry Turchinovich, Shixun Cao, Motoaki Bamba, Junichiro Kono

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


Exotic quantum vacuum phenomena are predicted in cavity quantum electrodynamics systems with ultrastrong light-matter interactions. Their ground states are predicted to be vacuum squeezed states with suppressed quantum fluctuations owing to antiresonant terms in the Hamiltonian. However, such predictions have not been realized because antiresonant interactions are typically negligible compared to resonant interactions in light-matter systems. Here we report an unusual, ultrastrongly coupled matter-matter system of magnons that is analytically described by a unique Hamiltonian in which the relative importance of resonant and antiresonant interactions can be easily tuned and the latter can be made vastly dominant. We found a regime where vacuum Bloch-Siegert shifts, the hallmark of antiresonant interactions, greatly exceed analogous frequency shifts from resonant interactions. Further, we theoretically explored the system’s ground state and calculated up to 5.9 dB of quantum fluctuation suppression. These observations demonstrate that magnonic systems provide an ideal platform for exploring exotic quantum vacuum phenomena predicted in ultrastrongly coupled light-matter systems.

Original languageEnglish
Article number3115
JournalNature communications
Issue number1
Publication statusPublished - 2021 Dec 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)


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