Substrate symmetry driven non-reciprocal acoustoelectric effect in SAW devices

Surface acoustic waves (SAWs) have become a versatile on-chip platform for studying spintronic topics, enabling dynamic coupling between strain, charge, and spin degrees of freedom. Among these, many studies report anomalous non-reciprocal acoustoelectric (AE) signals, often attributed to magnetic properties of thin films that were being studied. However, this assumes SAWs preserve time-reversal symmetry and cannot generate non-reciprocity on their own. Our work demonstrates that substrate symmetry and SAW propagation direction can independently induce apparent non-reciprocity. By systematically varying the substrate type and orientation, we experimentally reveal that the reciprocity of the AE effect is closely connected to the symmetry of the substrate under certain geometries and any deviation results in a possibility for non-reciprocal behavior. These findings highlight the need to account for device symmetry in SAW experiments and offer design guidelines for reliable spintronic measurements.