Shadow-free multimers as extreme-performance meta-atoms

TL;DR

This paper introduces shadow-free meta-atoms with extraordinary electromagnetic properties that can scatter incident energy directionally without forward scattering, enabling novel material behaviors.

Contribution

It generalizes parity-time symmetric structures to create lossless meta-atoms with zero forward scattering and controllable scattering directionality, surpassing traditional passive scatterer limitations.

Findings

Meta-atoms with zero forward scattering and controllable directionality.

Potential for creating materials with unusual electromagnetic properties.

Feasible microwave implementations with loaded dipole antennas.

Abstract

We generalize the concept of parity-time symmetric structures with the goal to create meta-atoms exhibiting extraordinary abilities to overcome the presumed limitations in the scattering of overall lossless particles, such as non-zero forward scattering and the equality of scattering and extinction powers for all lossless particles. Although the forward scattering amplitude and the extinction cross section of our proposed meta-atoms vanish, they scatter incident energy into other directions, with controllable directionality. These meta-atoms possess extreme electromagnetic properties not achievable for passive scatterers. As an example, we study meta-atoms consisting of two or three small dipole scatters. We consider possible microwave realizations in the form of short dipole antennas loaded by lumped elements. The proposed meta-atom empowers extraordinary response of a shadow-free scatterer and theoretically enables most unusual material properties when used as a building block of an artificial medium.