Unconventional Bose—Einstein Condensations from Spin-Orbit Coupling

According to the "no-node" theorem, the many-body ground state wavefunctions of conventional Bose-Einstein condensations (BEC) are positive-definite, thus time-reversal symmetry cannot be spontaneously broken. We find that multi-component bosons with spin-orbit coupling provide an unconven...

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Bibliographic Details
Published in:Chinese physics letters 2011-09, Vol.28 (9), p.097102-1-097102-4
Main Authors: Wu, Cong-Jun (从军 吴), Mondragon-Shem, Ian, Zhou, Xiang-Fa (祥发 周)
Format: Article
Language:English
Subjects:
Cold atoms
Condensates
Confining
Semiconductors
Spin-orbit interactions
Symmetry
Texture
Wavefunctions
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Summary:According to the "no-node" theorem, the many-body ground state wavefunctions of conventional Bose-Einstein condensations (BEC) are positive-definite, thus time-reversal symmetry cannot be spontaneously broken. We find that multi-component bosons with spin-orbit coupling provide an unconventional type of BECs beyond this paradigm. We focus on a subtle case of isotropic Rashba spin-orbit coupling and the spin-independent interaction. In the limit of the weak confining potential, the condensate wavefunctions are frustrated at the Hartree-Fock level due to the degeneracy of the Rashba ring. Quantum zero-point energy selects the spin-spiral type condensate through the "order-from-disorder" mechanism. In a strong harmonic confining trap, the condensate spontaneously generates a half-quantum vortex combined with the skyrmion type of spin texture. In both cases, time-reversal symmetry is spontaneously broken. These phenomena can be realized in both cold atom systems with artificial spin-orbit couplings generated from atom-laser interactions and exciton condensates in semi-conductor systems.
ISSN:0256-307X
1741-3540
DOI:10.1088/0256-307X/28/9/097102