Precise control over the localization of acoustic waves at microwave frequencies reveals new opportunities in emerging fields like quantum acoustics and spin mechanics. Conventional microwave acoustic resonators, engineered via phonon band structures, are prone to disturbances from fabrication defects, constraining their further development. Acoustic high-order topological insulators, known for their defect robustness and precise localization, have emerged as the preferred approach for developing high-performance resonators. However, the operating frequencies of existing acoustic high-order topological insulators have been limited to relatively low frequencies. Here, we present on-chip acoustic higher-order topological insulators (700–750 MHz) operating in the ultrahigh-frequency band, using lithium niobate nanomechanical metamaterials with smooth surfaces and sharp corners. By breaking the inversion symmetry of honeycomb lattices, higher-order valley Hall topological insulators featuring both odd-type and even-type corner states are constructed. Together, these advances promote the practical application of topological acoustics.

中文翻译：

---

Near GHz 铌酸锂高阶拓扑纳米力学超材料


精确控制微波频率下声波的定位，为量子声学和自旋力学等新兴领域带来了新的机会。传统的微波声学谐振器通过声子带结构设计，容易受到制造缺陷的干扰，限制了它们的进一步发展。声学高阶拓扑绝缘体以其缺陷鲁棒性和精确定位而闻名，已成为开发高性能谐振器的首选方法。然而，现有声学高阶拓扑绝缘体的工作频率被限制在相对较低的频率。在这里，我们展示了在超高频带工作的片上声学高阶拓扑绝缘体 （700–750 MHz），使用具有光滑表面和尖角的铌酸锂纳米机械超材料。通过打破蜂窝晶格的反演对称性，构建了同时具有奇数型和偶数型角态的高阶谷霍尔拓扑绝缘体。这些进步共同促进了拓扑声学的实际应用。