Unified Spin Electrodynamics of Dirac and Maxwell Fields

• Author / Creator

  Khosravi, Farhad

• Control and manipulation of the angular momentum of optical, electronic, or light-matter interacting systems has given rise to a myriad of applications. Majority of these applications, however, deploy only global angular momentum properties of these fields by solely incorporating far-field interactions or the conservation of total angular momentum. Local properties of optical and electronic fields and their interactions in the near field region have been gaining attention only recently and a thorough understanding of these dynamics is still essential.
  Here we study the angular momentum dynamics of light-matter interacting systems from a fundamental relativistic point of view. By applying Noether’s theorem to the quantum
  electrodynamics Lagrangian, we discover a local conservation of angular momentum equation applicable to far-field and near-field interactions. In contrast to the widely used
  duality symmetry approach towards the local conservation of helicity, our approach is quantum, relativistic, applies to light-matter interactions, does not introduce a new gauge field,
  and thus is experimentally testable. Our theory not only applies to the recent near-field and local light-matter experiments, but it also pushes the frontiers in light-matter interactions for the realization of next generations of experiments on the role of angular momentum.
  We further investigate the light-matter interacting system of an atom or a quantum dot coupled to the evanescent fields of a spherical resonator. We show that, due to the local alignment of the optical spin of the resonant modes and the radiated field of the source, the modes of the resonator are excited asymmetrically depending on the Zeeman transitions of the source. These results show the importance of local and near-field photonic spin in realizing on-chip quantum routing of single photons in quantum optical networks. Our work presents a generalization of universal spin-momentum locking of light to 3D structures. Moreover, we take the Dirac-Maxwell correspondence approach – the study of similarities between the Dirac and Maxwell’s equations – by presenting the solutions of Dirac equation for a cylindrical geometry. Labeled as Dirac wire, this geometry is the electronic analogue of an optical fiber. We have presented a set of new solutions for three types of Jackiw-Rebbi problems. We have studied the spatial distribution and global quantization of spin and orbital angular momentum in Dirac wire. We show that, as a result of the field confinement, a longitudinal angular momentum component emerges which is absent in previously know solutions of Dirac equation. Dirac wire can have important implications for spintronic applications.
  In addition, we demonstrate angular momentum properties of acoustic waves by solving for the Rayleigh surface acoustic waves (SAWs) propagating on a slab of Lithium Niobate. While these solutions are known, we show the spin-momentum locking property in the displacement field as well as the gyrating electric field of SAW and connect it to the spin-momentum locking observed in Dirac and Maxwell solutions of surface waves – highlighting the universality of this phenomenon.
  Finally, we study the implications of spin optomechanics for quantum vacuum radiation and quantum vacuum torque. By solving for a magnetic nanosphere spinning in the vicinity
  of a slab of a metallic or magnetic material, we find quantum vacuum radiation emerging from the magnetic sphere that is orders of magnitude larger than any other known material.
  We further show that the consequences of this large vacuum radiation or vacuum friction is experimentally observable for feasible and realistic setup parameters. These results are
  breakthrough for the field of quantum vacuum fluctuations proposing the first experimental observation of quantum vacuum radiation and quantum vacuum friction.
  Our results have important implications for the future of the fields of spin photonics and light-matter interactions. They provide insight for the understanding of the role of angular momentum in the local light-matter interactions and propose unique platforms for test and understanding of such interactions. Our work lays the foundation for future tabletop
  experiments for spin quantum electrodynamics.

• Subjects / Keywords

  • Quantum Optics
  • Photonics

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-4cwj-a840

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.