Integrating GHz surface acoustic waves with LaAlO₃/SrTiO₃-based mesoscopic devices

The LaAlO₃/SrTiO₃ (LAO/STO) interface hosts a gate-tunable superconducting two-dimensional electron system (2DES), a powerful platform for quantum devices such as ballistic electron waveguides and gate-controlled quantum dots. Here, long-range transfer of quantum information on a chip poses a significant challenge. Integrating surface acoustic waves (SAWs), which are piezoelectrically generated waves traveling along the surface of an elastic solid, with 2DES can potentially fulfill this requirement, offering a powerful route to control particle transport and explore acoustoelectric effects in quantum devices. In particular, SAWs in the GHz regime enable fast pumping of single particles. Although this effect is well- explored in GaAs based 2DES, SAW generation in SrTiO₃ remains largely unexplored due to the lack of intrinsic piezoelectricity at room temperature. Here, we investigate SAWs in LAO/STO and observe SAW modes up to 2.4 GHz with very low propagation loss (as small as 0.00632 dB/λ). To directly visualize these modes, we employ atomic acoustic force microscopy (AAFM), achieving sub-micron resolution imaging of the SAW wavefronts, providing insight into the electrostriction-induced SAW generation mechanism. Our results demonstrate controlled SAW excitation and nanoscale imaging of SAW modes, establishing a foundation for integrating SAWs with complex oxide 2DEGs for future acoustoelectric and quantum device applications.