Strong magnetism by closely spaced gold nanohoops

In this work, we show that closely-spaced gold nanohoops periodically distributed in a square lattice can provide a strong magnetic response in the near infrared regime when illuminated under normal incidence (perpendicular to the structure plane). Therefore, just a single metallic layer is needed to achieve the magnetic activity. A key point to achieve this response is that the aspect ratio must be higher than 1. Transmission and reflection spectra taken by means of a Fourier-Transform Infrared spectrometer show a strong absorbance peak at a wavelength that can be tuned by modifying the hole radius of the nanohoops or the underlying dielectric substrate. Numerical simulations show that at the resonance wavelength a virtual current loop is created, giving rise to a strong magnetic moment and a large magnetic field enhancement in the space between nanohoops.