Half-quantum vortex state in a spin-orbit-coupled Bose-Einstein condensate

B. Ramachandhran, Bogdan Opanchuk, Xia-Ji Liu, Han Pu, Peter D. Drummond, and Hui Hu
Phys. Rev. A 85, 023606 – Published 6 February 2012

Abstract

We theoretically investigate the condensate state and collective excitations of a two-component Bose gas in a two-dimensional harmonic trap subject to isotropic Rashba spin-orbit coupling. In the weakly interacting regime when the interspecies interaction is larger than the intraspecies interaction (g>g), we find that the condensate ground state has a half-quantum angular momentum vortex configuration with spatial rotational symmetry and skyrmion-type spin texture. Upon increasing the interatomic interaction beyond a threshold gc, the ground state starts to involve higher-order angular momentum components and thus breaks rotational symmetry. In the case of g<g, the condensate becomes unstable toward the superposition of two degenerate half-quantum vortex states. Both instabilities (at g>gc and g<g) can be determined by solving the Bogoliubov equations for collective density oscillations of the half-quantum vortex state and by analyzing the softening of mode frequencies. We obtain the phase diagram as a function of the interatomic interactions and the spin-orbit coupling. In addition, we directly simulate the time-dependent Gross-Pitaevskii equation to examine the dynamical properties of the system. Finally, we investigate the stability of the half-quantum vortex state against both trap anisotropy and anisotropy in the spin-orbit coupling.

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  • Received 6 January 2012

DOI:https://doi.org/10.1103/PhysRevA.85.023606

©2012 American Physical Society

Authors & Affiliations

B. Ramachandhran1, Bogdan Opanchuk2, Xia-Ji Liu2, Han Pu1, Peter D. Drummond2, and Hui Hu2

  • 1Department of Physics and Astronomy, and Rice Quantum Institute, Rice University, Houston, Texas 77251, USA
  • 2ARC Centres of Excellence for Quantum-Atom Optics and Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122, Australia

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Issue

Vol. 85, Iss. 2 — February 2012

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