Strong transient magnetic fields induced by THz-driven plasmons in graphene disks

TL;DR

This paper demonstrates that graphene disks can generate strong, transient magnetic fields at THz frequencies through plasmonic circular currents, enabling efficient control of light-induced magnetism in solid-state systems.

Contribution

The study introduces a method to induce and measure ultrafast magnetic fields in graphene disks via plasmonic resonances, offering tunable magnetic effects beyond material limitations.

Findings

Induced magnetic field strength of approximately 0.7 T.

Ultrafast Faraday rotation of about 1 degree observed.

Resonance frequency at 3.5 THz with high efficiency.

Abstract

Strong circularly polarized excitation opens up the possibility to generate and control effective magnetic fields in solid state systems, e.g., via the optical inverse Faraday effect or the phonon inverse Faraday effect. While these effects rely on material properties that can be tailored only to a limited degree, plasmonic resonances can be fully controlled by choosing proper dimensions and carrier concentrations. Plasmon resonances provide new degrees of freedom that can be used to tune or enhance the light-induced magnetic field in engineered metamaterials. Here we employ graphene disks to demonstrate light-induced transient magnetic fields from a plasmonic circular current with extremely high efficiency. The effective magnetic field at the plasmon resonance frequency of the graphene disks (3.5 THz) is evidenced by a strong (~1{\deg}) ultrafast Faraday rotation (~ 20 ps). In accordance with reference measurements and simulations, we estimated the strength of the induced magnetic field to be on the order of 0.7 T under a moderate pump fluence of about 440 nJ cm-2.