Monolithic On-Chip Phononic Chiral Anomalous Bulk States on LiNbO3 Thin-films

TL;DR

This paper demonstrates the first on-chip monolithic device utilizing chiral anomalous bulk states on LiNbO3 thin films, enabling highly efficient, unidirectional phononic waveguides with broad applications in signal processing and sensing.

Contribution

It introduces the first integrated monolithic CABS device on LiNbO3, combining topological robustness with on-chip integration for advanced phononic applications.

Findings

Unidirectional, low-loss phononic waveguides achieved

High transmission efficiency with broadband operation

Potential for high-fidelity microwave signal transmission

Abstract

Phononic materials are crucial for developing efficient, robust mechanical waveguides with strong transport properties, enabling advances in sensing, signal processing, energy harvesting, and microfluidics. A key motivation is their integration into monolithic systems for on-chip applications. While topological phononic materials developed in the past decade offer unidirectional edge states immune to backscattering, their integration requires large volumes to control localized small volumes' transport properties, limiting their efficiency and application in modern phononic circuits. The recently introduced chiral anomalous bulk states (CABSs) combine the advantages of topological materials with innovative boundary designs, overcoming transmission limitations and ensuring full material utilization for superior wave propagation. Here, we present the first on-chip monolithic CABS device integrated on a suspended LiNbO3 thin film. This breakthrough enables the creation of phononic waveguides with unmatched unidirectionality, low loss, and high transmission efficiency, seamlessly integrated with broadband piezoelectric transducers, and showcasing their potential for high-fidelity, broad-bandwidth microwave signal transmission. Additionally, we exploit the slow-wave characteristics of CABSs for delay lines and high-density signal processing. Tailoring wave propagation through boundary engineering opens a new paradigm for phononic/photonic device design, with implications across microelectronics, high-frequency communications, radar, and advanced sensing technologies. The work sets the stage for the future development of highly scalable, multifunctional, and robust phononic systems, unlocking new avenues for integrated acoustic technologies.