Vortex dynamics in spin-orbit-coupled Bose-Einstein condensates

Abstract

I use a time-dependent Lagrangian formalism and a variational trial function to study the dynamics of a two-component vortex in a spin-orbit-coupled Bose-Einstein condensate (BEC). For a single-component BEC, various experiments have validated this theoretical approach, for example a thermal quench that yields a quantized vortex in roughly 25% of trials [Freilich et al., Science 329, 1182 (2010)]. To be definite, I assume the specific spin-orbit form used by Lin and coworkers [Nature (London) 462, 628 (2009); Nature (London) 471, 83 (2011)] in recent NIST experiments, which introduces a spatial asymmetry because of the external Raman laser beams. I here generalize this formalism to include a two-component order parameter that has quantized circulation in each component but not necessarily with the same circulation. For example, a singly quantized vortex in just one component yields a BEC analog of the half-quantized vortex familiar in 3He-A and in p-wave chiral superconductors. This and other unusual two-component vortices have both periodic trajectories and unbounded trajectories that leave the condensate, depending on the initial conditions. The optimized phase of the order parameter induces a term in the particle current that cancels the contribution from the vector potential, leaving pure circulating current around the vortex.Received 18 December 2013DOI:https://doi.org/10.1103/PhysRevA.89.023629©2014 American Physical Society