Non-Hermitian dynamics and nonreciprocity of optically coupled nanoparticles

TL;DR

This paper explores the collective non-Hermitian dynamics of two optically coupled nanoparticles, demonstrating phenomena like parity-time symmetry breaking and mechanical lasing, with implications for nonequilibrium multi-particle systems.

Contribution

It introduces the use of tunable nonreciprocal optical interactions to study collective effects in nanoparticle systems, revealing new dynamical phases and transitions.

Findings

Observation of parity-time symmetry breaking

Identification of a collective mechanical lasing transition

Potential for controlling multi-particle nonequilibrium effects

Abstract

Non-Hermitian dynamics, as observed in photonic, atomic, electrical, and optomechanical platforms, holds great potential for sensing applications and signal processing. Recently, fully tunable nonreciprocal optical interaction has been demonstrated between levitated nanoparticles. Here, we use this tunability to investigate the collective non-Hermitian dynamics of two nonreciprocally and nonlinearly interacting nanoparticles. We observe parity-time symmetry breaking and, for sufficiently strong coupling, a collective mechanical lasing transition, where the particles move along stable limit cycles. This work opens up a research avenue of nonequilibrium multi-particle collective effects, tailored by the dynamic control of individual sites in a tweezer array.