Klein tunneling and supercollimation of pseudospin-1 electromagnetic waves

TL;DR

This paper demonstrates that pseudospin-1 electromagnetic waves in certain photonic crystals exhibit unique tunneling and collimation behaviors, offering new methods for controlling photon transport through their distinct wave scattering properties.

Contribution

It introduces a pseudospin-1 framework for describing wave propagation in photonic crystals with conical dispersions, revealing novel transport phenomena like Klein tunneling and supercollimation.

Findings

Pseudospin-1 eigenmodes can be described by an effective spin-orbit Hamiltonian.

Distinct boundary conditions lead to new wave transport behaviors.

Pseudospin-1 allows easier collimation compared to pseudospin-1/2.

Abstract

Pseudospin plays a central role in many novel physical properties of graphene and other artificial systems which have pseudospins of 1/2. Here we show that in certain photonic crystals (PCs) exhibiting conical dispersions at k = 0, the eigenmodes near the "Dirac-like point" can be described by an effective spin-orbit Hamiltonian with a pseudospin of 1, treating wave propagations in the upper cone, the lower cone and a flat band (corresponding to zero refractive index) within a unified framework. The 3-component spinor gives rise to boundary conditions distinct from those of pseudospin-1/2, leading to new wave transport behaviors as manifested in Klein tunneling and supercollimation. For example, collimation can be realized more easily with pseudospin-1 than pseudospin-1/2. The special wave scattering properties of pseudospin-1 photons, coupled with the discovery that the effective photonic "potential" can be varied by a simple change of length scale, may offer new ways to control photon transport.