Optimizing Phononic Crystal Waveguides for Enhanced Surface Acoustic Wave Confinement

Through the use of strain and induced piezoelectric fields, surface acoustic waves (SAWs) have been shown to control quantum information processes, such as single photon emission and the coherent transport of electron spins. Regarding the latter, systems using plane surface waves have provided suitable demonstration systems, but to build complexity, more control over the acoustic wave may be required. One method for acoustic control is the use of phononic crystals consisting of periodic arrays of nanofabricated holes on the surface of a device. These inclusions form a metamaterial-like layer with properties different from the host material to dictate the physics of wave motion. Exploiting these surface properties can lead to acoustic waveguides, which can be designed to control the path of the SAWs. The design parameters of a new type of phononic crystal waveguide are explored that use twofold elliptical cylinder inclusions to create a slow region that also limits coupling and radiative loss to bulk acoustic modes. Such a waveguide will be the foundational piece in an acoustic circuit that can then mediate complex spin transport geometries.