Unconventional Bose—Einstein Condensations from Spin-Orbit Coupling

Chinese Physics Letters (Impact Factor: 0.95). 09/2008; 28(9). DOI: 10.1088/0256-307X/28/9/097102
Source: arXiv

ABSTRACT According to the "no-node" theorem, 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 the 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.

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    Nature Communications 05/2014; 5:4023. DOI:10.1038/ncomms5023
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    ABSTRACT: In this paper, we prove analytically that the plane-wave Bose-Einstein condensates with spin-orbit coupling are stable in two dimensions at zero temperature. The SOC induced extra breaking of the O(2) symmetry of the ground state makes the goldstone modes more divergent in the infrared limit. But the depletions are still finite, which means the condensates are stable.
    The European Physical Journal D 03/2013; 67(3). DOI:10.1140/epjd/e2012-30198-9
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    Physical Review A 12/2009; 81(4). DOI:10.1103/PhysRevA.81.043601


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