An inverse Faraday effect through linear polarized light

TL;DR

This paper demonstrates a novel inverse Faraday effect induced by linearly polarized light in plasmonic nanostructures, enabling on-demand, strong, stationary magnetic fields at the nanoscale with potential applications in ultrafast magnetic control.

Contribution

It introduces the concept of linear polarization inducing the inverse Faraday effect via plasmonic nano-antennas, a phenomenon previously thought exclusive to elliptical or circular polarization.

Findings

Linear polarization can generate a non-zero magnetic field via IFE in plasmonic nanostructures.

The magnetic field strength is 25 times greater than that produced by circular polarization.

Magnetic field orientation can be flipped by changing the incident polarization angle.

Abstract

The inverse Faraday effect (IFE) allows the generation of magnetic fields by optical excitation only. Since its discovery in the 60s, it was believed that only an elliptical or circular polarization could magnetize matter by this magneto-optical phenomenon. Here, we demonstrate the generation of an IFE via a linear polarization of light. This new physical concept results from the local manipulation of light by a plasmonic nano-antenna. We demonstrate that a gold nanorod excited by a linear polarization generates a non-zero magnetic field by IFE when the incident polarization of the light is not parallel to the long axis of the rod. We show that this dissymmetry generates hot spots of local non-vanishing spin densities (local elliptical polarization state), introducing the concept of super circular light, allowing this magnetization. Moreover, by varying the angle of the incident linear polarization with respect to the nano-antenna, we demonstrate the on-demand flipping of the magnetic field orientation. Finally, this linear IFE generates a stationary magnetic field 25 times stronger than what a gold nanoparticle produces when excited by a circular polarization and via a classical IFE. The creation of stationary magnetic fields by IFE in a plasmonic nanostructure is nowadays the only technique allowing the creation of ultra-short, intense magnetic field pulses at the nanoscale. Thus, it finds applications in the ultrafast control of magnetic domains with applications not only in data storage technologies but also in research fields such as magnetic trapping, magnetic skyrmion, magnetic circular dichroism, to spin control, spin precession, spin currents, and spin waves, among others.