# Far-field phonon coupling in valley metamaterial circuits

## TL;DR

Researchers demonstrated a new way to couple phonons over long distances using a special metamaterial structure, enabling better control of sound waves on chips.

## Contribution

The novel contribution is the experimental realization of broadband far-field phonon coupling in valley metamaterial circuits.

## Key findings

- Far-field phonon coupling was confirmed over distances up to five wavelengths using transmission spectroscopy.
- Multiplexed coupling pathways were enabled, overcoming limitations of near-field coupling.
- Non-Hermitian dynamics were controlled through loss and distance modulation in the system.

## Abstract

On-chip whispering-gallery-mode cavities enable versatile bosonic wave manipulation but typically rely on near-field evanescent coupling. Here we experimentally demonstrate broadband far-field phonon coupling in a valley metamaterial cavity integrated with a Dirac-cone waveguide—termed a “Dirac strip”. The far-field coupling is confirmed by transmission spectroscopy and spatiotemporal field mapping over distances up to approximately five wavelengths, enabling multiplexed, distance-robust coupling pathways that overcome near-field limitations. By combining near-field and far-field cavities on the same substrate, we achieve amplification and control of non-Hermitian dynamics through loss and distance modulation of sympathetic resonances, directly resolved via piezo-laser interferometry. This work establishes a scalable phononic platform for far-field coupling and paves the way for parallel topological wave processors.

Here, authors experimentally demonstrate broadband far-field phonon coupling in a valley metamaterial integrated with a Dirac-strip, achieving coupling at a five-wavelength distance.