Numerical study of magneto-optical binding between two dipolar particles under illumination by two counter-propagating waves

TL;DR

This theoretical study explores magneto-optical binding between two dipolar nanoparticles under counter-propagating waves, revealing how magnetic fields influence resonant forces, spins, and system symmetry, advancing control over optical matter.

Contribution

It provides a comprehensive description of photonic coupling in magneto plasmonic dimers under arbitrary magnetic fields, extending previous models to include non-reciprocal effects and mechanical observables.

Findings

Resonant radiation pressure appears when magnetic fields break symmetry.

Tunable inter-particle forces and spins are demonstrated.

Mechanical observables reveal detailed system information.

Abstract

The formation of a stable magneto plasmonic dimer with THz resonances is theoretically studied for the principal directions of the system. Unlike a recent report, our work provides a complete description of the full photonic coupling for arbitrary magnetic fields as, for instance, unbalanced particle spins. As an illustration, we consider two small, n-doped InSb nanoparticles under illumination by two counter-propagating plane waves. Remarkably, when an external magnetic field exists, the symmetry in the system is broken, and a resonant radiation pressure for the dimer appears. Similarly, tunable inter-particle forces and spins are exerted on the non-reciprocal dimer. The system is also characterized when the magnetic field is absent. Moreover, we show how the mechanical observables truly characterize the dimer since their resonance dependency contains detailed information about the system. Unlike far-field observables like absorption, mechanical magnitudes depend on the system's near-field. In addition, the nature of the particle spins is originally explained by the energy flow's behavior around the dimer. This work constitutes a generalization of any previous approach to optical binding between small nanoparticles. It paves the way for fully controlling optical matter and nano factory designs based on surface plasmon polaritons.