摘要
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.
作者
WU Cong-Jun
Ian Mondragon-Shem
ZHOU Xiang-Fa
吴从军;Ian Mondragon-Shem;周祥发(Department of Physics,University of California,San Diego,CA 92093;Instituto de Física,Universidad de Antioquia,AA 1226,Medellín,Colombia;Key Laboratory of Quantum Information,University of Science and Technology of China,Hefei 230026)
基金
by US NSF-DMR 1105945 and AFOSR-YIP program.X.F.Z.acknowledges the support of CUSF,,SRFD(20103402120031)and the China Postdoctoral Science.
