UNCONVENTIONAL BOSE-EINSTEIN CONDENSATIONS BEYOND THE "NO-NODE" THEOREM

作者：Wu Congjun^*

来源：Modern Physics Letters B, 2009, 23(1): 1-24.

DOI：10.1142/s0217984909017777

• Bose-Einstein condensation
• optical lattices
• exciton
• time-reversal symmetry
• spontaneous symmetry breaking

Feynman';s "no-node" theorem states that the conventional many-body ground state wavefunctions of bosons in the coordinate representation are positive definite. This implies that time-reversal symmetry cannot be spontaneously broken. In this article, we review our progress in studing a class of new states of unconventional Bose-Einstein condensations beyond this paradigm. These states can either be the long-lived metastable states of ultracold bosons in high orbital bands in optical lattices as a result of the "orbital Hund';s rule" interaction, or the ground states of spinful bosons with spin-orbit coupling linearly dependent on momentum. In both cases, Feynman';s argument does not apply. The resultant many-body wavefunctions are complex-valued and thus break time-reversal symmetry spontaneously. Exotic phenomena in these states include the Bose-Einstein condenstion at nonzero momentum, the ordering of orbital angular momentum moments, the half-quantum vortex, and the spin texture of skyrmions.

• 出版日期2009-1-10