Quantum magnonics

Abstract:

We demonstrate the efficient excitation of spin waves in the ultralow magnetic damping material yttrium iron garnet (YIG) by surface acoustic waves (SAWs). To this end, we use interdigital transducers fabricated on a piezoelectric zinc oxide (ZnO) thin film covering the YIG. This enables the excitation of coherent, propagating Rayleigh-type and Sezawa-type SAWs. We find that the ultralow magnetic damping of YIG is retained after the $\mathrm{Zn}\mathrm{O}$ deposition and we perform a comprehensive investigation of the magnetoelastic interaction due to the different SAW modes as a function of the external magnetic field magnitude and orientation. By measuring the SAW attenuation, our experiments reveal a highly anisotropic and nonreciprocal SAW–spin-wave interaction in agreement with our model calculation, while demonstrating that low-damping magnons can be efficiently excited by SAWs.

Abstract:

<jats:p>We study surface acoustic waves (SAWs) in yttrium iron garnet (YIG)/zinc oxide (ZnO) heterostructures, comparing the results of a computationally lightweight analytical model with time-resolved microfocused Brillouin light scattering (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mtext fontfamily="times">μ</a:mtext></a:math>-BLS) data. Interdigital transducers (IDTs), with operational frequencies in the gigahertz regime, were fabricated on 50-nm and 100-nm thin films of YIG prior to sputter deposition of 830-nm and 890-nm films of piezoelectric ZnO. We find good agreement between our analytical model and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><e:mtext fontfamily="times">μ</e:mtext></e:math>-BLS data of the IDT frequency response and SAW group velocity, with clear differentiation between the Rayleigh-like and Sezawa-like modes. Finally, nonreciprocal coupling between SAWs and spin waves (SWs) is shown. This work paves the way for a detailed study of the interaction between SAWs and SWs in low SW damping YIG, with the possibility of a method for future energy-efficient SW excitation.</jats:p> <jats:sec> <jats:title/> <jats:supplementary-material> <jats:permissions> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material> </jats:sec>