Unveiling pseudospin and angular momentum in photonic graphene

Abstract

Pseudospin, an additional degree of freedom inherent in graphene, plays a key role in understanding many fundamental phenomena such as the anomalous quantum Hall effect, electron chirality and Klein paradox. Unlike the electron spin, the pseudospin was traditionally considered as an unmeasurable quantity, immune to Stern-Gerlach-type experiments. Recently, however, it has been suggested that graphene pseudospin is a real angular momentum that might manifest itself as an observable quantity, but so far direct tests of such a momentum remained unfruitful. Here, by selective excitation of two sublattices of an artificial photonic graphene, we demonstrate pseudospin-mediated vortex generation and topological charge flipping in otherwise uniform optical beams with Bloch momentum traversing through the Dirac points. Corroborated by numerical solutions of the linear massless Dirac-Weyl equation, we show that pseudospin can turn into orbital angular momentum completely, thus upholding the belief that pseudospin is not merely for theoretical elegance but rather physically measurable.

12 pages, 5 figures

References in corpus (7)

• The electronic properties of graphene
• Chiral tunneling and the Klein paradox in graphene
• Multi-Component Quantum Gases in Spin-Dependent Hexagonal Lattices
• Extremal transmission at the Dirac point of a photonic band structure
• Two-dimensional Mott-Hubbard electrons in an artificial honeycomb lattice
• Engineering artificial graphene in a two-dimensional electron gas
• Making Massless Dirac Fermions from Patterned Two-Dimensional Electron Gases

Cited by in corpus (11)

• Topological Photonics
• Electron-phonon scattering and in-plane electric conductivity in twisted bilayer graphene
• Generating Lieb and super-honeycomb lattices by employing the fractional Talbot effect
• Asymmetric conical diffraction in dislocated edge-centered square lattices
• Modeling the optical properties of Twisted Bilayer Photonic Crystals
• Type-II Dirac photonic lattices
• Angular momentum anisotropy of Dirac carriers: A new twist in graphene
• Topological phenomena demonstrated in photorefractive photonic lattices
• Generating electromagnetic modes with fine tunable orbital angular momentum by planar topological circuits
• Spin-orbit coupling in photonic graphene
• Higher-order Quantum Spin Hall Effect of Light