Micro- and nanomechanical systems with exceptionally low dissipation rate have gained extensive interests because of their excellent performance in precise metrology, such as force/mass microscopy, time keeping, and quantum transduction1. In the last ten years, large progress has been made in understanding the dissipation mechanisms of mechanical systems, and new dissipation engineering techniques of soft clamping and strain engineering have been discovered. The latter have led to amazing achievements such as mechanical resonators with quality factors up to 10 billion at cryogenic temperature and up to 3.6 billion at room temperature. In addition to mechanical resonators, mechanical (phononic) waveguides are another fundamental building block. Similar to electrical wires and optical waveguides, they allow information transfer via phononic waves and then form a phononic circuit. Phononic waveguides have been established as good interconnect channels among different physical systems due to their direct and strong coupling to electrical, optical, and even spin systems, and also been proved practical for quantum signal transport. However, the state-of-art dissipation engineering techniques still have not been investigated in phononic waveguiding systems, and their large loss remains their major limitation preventing them from wide applications in physics and engineering.
Topological insulator is a new phase of matter that is electrically insulating inside the bulk but conductive on the surface. In the last five years, the concept of topology has been extended to the realm of phononics, which has overturned some of the traditional views on wave propagation and manipulation. Most importantly, it can be adapted to realize topologically protected backscattering-immune phonon transport, which remains a grand challenge for conventional schemes while building large systems. However, the existing topological phononic systems also show limitations due to their large dissipation. Luckily, the crystal structure of topological phononic devices makes them extremely suitable to employ the state-of-art dissipation engineering techniques for realizing extremely low loss. Such a combination has not been experimentally realized to date.
This project will merge the fields of dissipation engineering and topological phononics to construct a mechanical waveguiding channel with unprecedentedly low dissipation. The major objective is to reduce the loss of phononic waveguides by orders of magnitude such that elastic waves propagate over several meters, and then demonstrate applications of them for classical and quantum signal exchange between separate physical (electrical, optical, or mechanical) systems.
