Position, spin, and orbital angular momentum of a relativistic electron
Abstract
Motivated by recent interest in relativistic electron vortex states, we revisit the spin and orbital angular momentum properties of Dirac electrons. These are uniquely determined by the choice of the position operator for a relativistic electron. We consider two main approaches discussed in the literature: (i) the projection of operators onto the positiveenergy subspace, which removes the Zitterbewegung effects and correctly describes spinorbit interaction effects, and (ii) the use of NewtonWignerFoldyWouthuysen operators based on the inverse FoldyWouthuysen transformation. We argue that the first approach [previously described in application to Dirac vortex beams in K. Y. Bliokh et al., Phys. Rev. Lett. 107, 174802 (2011), 10.1103/PhysRevLett.107.174802] has a more natural physical interpretation, including spinorbit interactions and a nonsingular zeromass limit, than the second one [S. M. Barnett, Phys. Rev. Lett. 118, 114802 (2017), 10.1103/PhysRevLett.118.114802].
 Publication:

Physical Review A
 Pub Date:
 August 2017
 DOI:
 10.1103/PhysRevA.96.023622
 arXiv:
 arXiv:1706.01658
 Bibcode:
 2017PhRvA..96b3622B
 Keywords:

 Quantum Physics
 EPrint:
 10 pages, 1 table, to appear in Phys. Rev. A