Parity-time symmetry from stacking purely dielectric and magnetic slabs

TL;DR

This paper demonstrates how Parity-time symmetry can be achieved in photonic structures by stacking dielectric and magnetic slabs, leading to phase transitions and potential for ultrathin metamaterials with unique reflection properties.

Contribution

It introduces a novel approach to Parity-time symmetry involving combined mirror symmetry and electric-magnetic coupling, extending the concept to multi-material potentials.

Findings

Band structure undergoes phase transition with gain/loss variation.

Exceptional points appear in the long wavelength limit.

Ultrathin metamaterials with unidirectional reflection can be designed.

Abstract

We show that Parity-time symmetry in matching electric permittivity to magnetic permeability can be established by considering an effective Parity operator involving both mirror symmetry and coupling between electric and magnetic fields. This approach extends the discussion of Parity-time symmetry to the situation with more than one material potential. We show that the band structure of a one-dimensional photonic crystal with alternating purely dielectric and purely magnetic slabs can undergo a phase transition between propagation modes and evanescent modes when the balanced gain/loss parameter is varied. The cross-matching between different material potentials also allows exceptional points of the constitutive matrix to appear in the long wavelength limit where they can be used to construct ultrathin metamaterials with unidirectional reflection.