Progress in numerical modeling of near-field infrared phenomena at nanometer length scales*

The extraction of meaningful nanoscale material properties is reliant on proper modeling of the experimental spectra obtained with broadband, near-field infrared nanospectroscopy. We will discuss our progress towards this goal by presenting combined experimental and numerical modeling results on materials with diverse properties and geometries.. Strong coupling of light to the probe-sample system in highly polar dielectrics such as SrTiO₃ leads to multiple phonon-polariton resonances. We show that these resonances should be described by detailed numerical simulations¹. We obtain near-field infrared spectra on Cu₂S nanoplatelets and show that numerical modeling of the spectra is indispensable for obtaining the properties of nanomaterials. Furthermore, many materials have anisotropic dielectric functions. We have obtained near-field infrared spectra on a uniaxial rutile TiO₂ crystal. Proper modeling of spectra from anisotropic materials also requires meticulous numerical simulations.

¹ P. McArdle, D.J. Lahneman, A. Biswas, F. Keilmann, and M.M. Qazilbash, Phys. Rev. Res. 2, 023272 (2020).