Observation of Nonreciprocal Diffraction of Surface Acoustic Wave

The rectification phenomenon caused by the simultaneous breaking of time-reversal and spatial inversion symmetries has been extended to a wide range of (quasi)particles and waves; however, nonreciprocal diffraction, which is the imbalance of upward and downward deflections, was previously observed only for photons and remained to be extended to other (quasi)particles. In this Letter, we present evidence of the nonreciprocal diffraction of a surface acoustic wave (SAW) utilizing a magnetoelastic grating on a SAW device. Asymmetric diffraction intensities were observed when the ferromagnetic resonance was acoustically excited. Based on a theoretical model, we attribute the microscopic origin of this phenomenon to the resonant scattering involving ferromagnetic resonance excitations. The novel property may pave an avenue to further development of SAW devices for various purposes, including microwave communications and quantum engineering applications.