Fig. 4: Comparison of effective electromechanical coupling coefficient \({k}_{t}^{2}\) between this work and the state-of-the-art reported acoustic resonators.
From: Twist piezoelectricity: giant electromechanical coupling in magic-angle twisted bilayer LiNbO3
*The formula for calculating \({k}_{t}^{2}\) in ref. 43 was \({k}_{t}^{2}={\pi f}_{\!\!r}/{2f}_{a}/\tan (\frac{{\pi f}_{r}}{{2f}_{a}})\), which was different with formula used in this work and the others [\({k}_{t}^{2}={\pi }^{2}/8\) \(({f}_{\!\!a}^{2}-{f}_{\!\!r}^{2})|{f}_{\!\!r}^{2}\)]. According to the result in ref. 43, which is 43%, the ratio of \({f}_{r}/{f}_{a}\) was 0.7869, and the unified result in this figure should be 75.9%. **The resonator in ref. 58 was fabricated on the bulk Y27.5 Lithium Niobate substrate, on which the resonate frequency was on the megahertz scale (MHz).
