Pico-photonics: Anomalous Atomistic Waves in Silicon

The concept of photonic frequency $(\omega)$ - momentum $(q)$ dispersion has been extensively studied in artificial dielectric structures such as photonic crystals and metamaterials. However, the $\omega-q$ dispersion of electrodynamic excitations hosted in natural materials at the atomistic level is far less explored. Here, we develop a Maxwell Hamiltonian theory of matter combined with the quantum theory of atomistic polarization to obtain the electrodynamic dispersion of natural materials interacting with the photon field. We apply this theory to silicon and discover the existence of anomalous atomistic waves. These waves occur in the spectral region where propagating waves are conventionally forbidden in a macroscopic theory. Our findings demonstrate that natural media can host a variety of yet to be discovered waves with sub-nano-meter effective wavelengths in the pico-photonics regime.