# Synthetic gauge fields for phonon transport in a nano-optomechanical system

## TL;DR

This paper demonstrates a scalable on-chip optomechanical system that creates synthetic magnetic gauge fields for phonons, enabling nonreciprocal transport and paving the way for topological acoustic phases.

## Contribution

It introduces a novel method to generate magnetic gauge fields for phonons using multimode optomechanical interactions in a dynamically modulated system.

## Key findings

- Observation of nonreciprocal phonon transport mimicking Aharonov-Bohm effect
- The scheme does not require high-quality cavities, allowing scalability
- Potential to explore topological acoustic phases in complex systems

## Abstract

Gauge fields play important roles in condensed matter, explaining for example nonreciprocal and topological transport phenomena. Establishing gauge potentials for phonon transport in nanomechanical systems would bring quantum Hall physics to a new domain, which offers broad applications in sensing and signal processing, and is naturally associated with strong nonlinearities and thermodynamics. In this work, we demonstrate a magnetic gauge field for nanomechanical vibrations in a scalable, on-chip optomechanical system. We exploit multimode optomechanical interactions, which provide a useful resource for the necessary breaking of time-reversal symmetry. In a dynamically modulated nanophotonic system, we observe how radiation pressure forces mediate phonon transport between resonators of different frequencies, with a high rate and a characteristic nonreciprocal phase mimicking the Aharonov-Bohm effect. We show that the introduced scheme does not require high-quality cavities, such that it can be straightforwardly extended to explore topological acoustic phases in many-mode systems resilient to realistic disorder.