[Zhang, Guang-Ming] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China; [Lee, Dung-Hai] Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA; [Lee, Dung-Hai] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Mat Sci, Berkeley, CA 94720 USA; [Xiang, Tao] Chinese Acad Sci, Inst Phys, Beijing 100190, Peoples R China; [Xiang, Tao] Chinese Acad Sci, Inst Theoret Phys, Beijing 100190, Peoples R China
英文摘要:
We show that there is a topological (Berry phase) term in the non-linear sigma model description of the SO(5) spin chain. It distinguishes the linear and projective representations of the SO(5) symmetry group, in exact analogy to the well-known theta-term of the SO(3) spin chain. The presence of the topological term is due to the fact that pi(2)(SO(5)/SO(3) x SO(2)) = Z. We discuss the implication of our results on the spectra of the SO(5) spin chain, and connect it with a recent solvable SO(5) spin model which exhibits valence bond solid ground state and edge degeneracy. (c) 2011 Elsevier B.V. All rights reserved.
