Title: Chiral Phonons and Phononic Birefringence in Ferromagnetic Metal – Bulk Acoustic Resonator Hybrids
When: Tuesday, September 05, 2023, 12:00.
Place: Department of Theoretical Condensed Matter Physics, Faculty of Sciences, Module 5, Seminar Room (5th Floor).
Speaker: Dr. Matthias Althammer, Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany, Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany.
Magnomechanical devices, in which magnetic excitations couple to mechanical vibrations, have been discussed as efficient and broadband microwave signal transducers in the classical and quantum limit. Early experiments [1,2,3] focused on the ultra-low magnetization damping material yttrium iron garnet Y3Fe5O12, YIG) grown lattice matched on gadolinium gallium garnet (Gd3Ga5O12, GGG) substrates. However, the constraint to GGG substrates is far from ideal as GGG has unfavorable acoustic and magnetic properties especially at low temperatures.
We experimentally investigate the resonant magnetoelastic coupling between the ferromagnetic resonance (FMR) modes in metallic Co25Fe75 thin films, featuring ultra-low magnetic damping as well as sizable magnetostriction, and standing transverse elastic phonon modes in sapphire, silicon and gadolinium gallium garnet at cryogenic temperatures [4]. For all substrates, we observe a coherent interaction between the acoustic and magnetic modes. We identify the phonon modes as transverse shear waves propagating with slightly different velocities ), i.e., all investigated substrates show potential for phononic birefringence as well as phonon mediated angular momentum transport. Our magnon-phonon hybrid systems operates in a coupling regime analogue to the Purcell enhanced damping in cavity-magnonics.
References
- K. An et al., Phys. Rev. B 101, 060407 (2020).
- K. An et al., Phys. Rev. X 12, 011060 (2022).
- R. Schlitz et al., Phys. Rev. B 106, 014407 (2022).
- M. Müller et al., arXiv:2303.08429 (2023).
