Designing magnonic crystals for quantum control*

Ferromagnetic materials provide excellent opportunites for strong hybridization between microwave photons and spin excitations, as the collective motion of exchange-locked spins enhances light-matter coupling[1,2]. Quantum control of this coupling is eased through the ability to electrically manipulate the energy of spin excitations, bringing them into and out of resonance with microwave photons. Electric fields applied to insulating magnets can efficiently change spin excitation energies, without the dissipation produced with electrical current-induced manipulation. The Dzyaloshinskii-Moriya interaction provides an approach to manipulate spin excitations with electric fields, and has been demonstrated in yttrium iron garnet. The small effect seen in bulk magnets, well described by theoretical calculations[3], can be dramatically enhanced by patterning the ferromagnetic insulating material into one-dimensional and two-dimensional magnonic crystals. It is then possible to shift the magnonic gaps into and out of resonance with a microwave cavity using an electric field, paving the way for a fully quantum switch that works via voltages, not currents, and has nearly no dissipation. This will benefit coherent quantum transduction between electric, magnetic, and electromagnetic degrees of freedom in a quantum device.

[1] "Strong field interactions between a nanomagnet and a photonic cavity", O. O. Soykal and M. E. Flatté, PRL 104, 077202 (2010)
[2] "Size dependence of strong coupling between nanomagnets and photonic cavities", O. O. Soykal and M. E. Flatté, PRB 82, 104413 (2010)
[3] "Electric field Coupling to Spin Waves in a Centrosymmetric Ferrite", X. Zhang, T. Liu, M. E. Flatté and H. X. Tang, PRL 113, 037202 (2014)
[4] "Electric field control of magnon gaps in a ferromagnet using a spatially-periodic electric field", G. Sietsema, T. Liu, and M. E. Flatté, SPIN vol. 7, 1740012 (2017)