Topological Light Nodal Lines in FCC Lattice

TL;DR

This paper reveals that face-centered-cubic (fcc) photonic crystals can host topologically nontrivial nodal lines in momentum space, leading to slow-light interface states with potential experimental confirmation of topological photonic states.

Contribution

It introduces the concept of topological nodal lines in fcc photonic crystals and links them to observable slow-light interface states, a novel topological photonic phenomenon.

Findings

Existence of topological nodal lines in fcc photonic crystals.

Correspondence between photonic pseudogaps and nodal lines.

Potential for experimental verification of topological photonic states.

Abstract

Light cone with the speed of light independent of its wavelength in vacuum has been known for long time. In the present work, we unveil that in a face-centered-cubic (fcc) lattice of dielectric spheres novel light cones can be created over closed loops in momentum space, dubbed as nodal lines (NL), and that as a consequence of the nontrivial topology of NL interface states with a drumhead-shaped band structure appear where light can be slowed down significantly. We discuss that photonic pseudogaps found in previous experimental and theoretical studies for fcc photonic crystals are consistent with the present finding of NL. This offers a unique chance to confirm the existence of NL as a novel topological state.