Wei Han, Suying Zhang, Wu-Ming Liu
We investigate ground-state structures of spin-orbit coupled Bose-Einstein condensates in spin-dependent optical lattices. Our results show that the competition between the spin-orbit coupling and the optical lattice leads to three distinct phases---density stripe, triangular vortex lattice and rectangular vortex lattice. In the density stripe phase, the condensates act as alternately arranged spin domains, and the domain wall responses to spin-orbit coupling with its structure changing from N\'{e}el wall to Bloch wall. In the vortex lattice phases, both the triangular and rectangular lattices are composed of alternately arranged vortex and antivortex chains, with alternating-direction plane waves propagating on two sides of each chain. We demonstrate that the exotic vortex phase is essentially equivalent to a lattice composed of meron pairs and antimeron pairs in the pseudospin representation. Furthermore, we discuss how to observe these phases in future experiments.
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http://arxiv.org/abs/1211.2097
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