Magnetic moment generation in small gold nanoparticles via the plasmonic inverse Faraday effect

TL;DR

This paper presents a theoretical study showing that circularly polarized laser light can induce a significant magnetic moment in small gold nanoparticles through a plasmonic inverse Faraday effect, involving collective electron dynamics.

Contribution

It introduces a semiclassical quantum hydrodynamic model to explain how circularly polarized light generates magnetic moments in gold nanoparticles, highlighting the plasmonic inverse Faraday effect as the key mechanism.

Findings

Magnetic moments of about 0.35 μB/atom induced at 450 GW/cm² laser intensity

The effect is driven by a plasmonic, orbital inverse Faraday effect involving surface electron currents

The model incorporates quantum many-body and nonlocal effects for accurate predictions

Abstract

We theoretically investigate the creation of a magnetic moment in gold nanoparticles by circularly polarized laser light. To this end, we describe the collective electron dynamics in gold nanoparticles using a semiclassical approach based on a quantum hydrodynamic model that incorporates the prin- cipal quantum many-body and nonlocal effects, such as the electron spill-out, the Hartree potential, and the exchange and correlation effects. We use a variational approach to investigate the breathing and the dipole dynamics induced by an external electric field. We show that gold nanoparticles can build up a static magnetic moment through the interaction with a circularly polarized laser field. We analyze that the responsible physical mechanism is a plasmonic, orbital inverse Faraday effect, which can be understood from the time-averaged electron current that contains currents rotating on the nanoparticles surface. The computed laser-induced magnetic moments are sizeable, of about 0.35 muB/atom for a laser intensity of 450 GW/cm2 at plasmon resonance.