Pablo Cerrato-Serrano

Evolution of cavity magnon polartions across the ferromagnetic phase transition in van der Waals magnet Cr2Ge2Te6

Hybrid systems in condensed matter physics are platforms where several quasiparticles can interact giving rise to new phenomena and interesting properties that cannot be obtained by the composing quasiparticles alone. These systems have found applications in the sensor industry [1], and quantum measurements of qubits [2], among others. In this work, we study the interaction of microwave cavity photons and magnons (collective spin excitation). When these particles interact strongly, they hybridize and form magnon polaritons.

We demonstrate the use of cavity magnon polaritons as a spectroscopic probe to investigate the evolution across the ferromagnetic-to-paramagnetic transition in van der Waals magnet Cr2Ge2Te6 [3]. Using cavity microwave transmission spectroscopy from temperatures of 5 K to 100 K, we observe pronounced avoided crossings with GHz collective coupling strengths and reaching a peak cooperativity of 1.45 within the ferromagnetic phase, establishing the strong-coupling regime. Our results [4] certify cavity magnon-polariton spectroscopy as a sensitive, non-invasive probe of spin order, dissipation and phase-transition dynamics in two-dimensional van der Waals magnets.

References:

[1] Cao, Y. et al, Phys. Rev. B 99, 214415 (2019)

[2] Dey, A., Phys. Rev. A 114, 033724 (2026)

[3] Gong, C. et al, Nature 546, 7657 (2017)

[4] Cerrato-Serrano, P. et al, in preparation.