title: Nonlocal topological order in antiferromagnetic Heisenberg chains.
abstract: We demonstrate the existence of nonlocal topological (string) order in half-integer-spin antiferromagnetic Heisenberg chains on macroscopic scale on the basis of analytical scaling analysis and density matrix renormalization group calculations. Strong numerical evidence leads to a conjecture that chains with S = (2m-1)/2 and m (m = integers) belong to the same topological class defined by the topological angle theta/pi = 1/m that plays a role similar to the fictitious gauge field in the fractional quantum Hall effect.
authors.affiliation: Institute of Theoretical Physics, P.O. Box 2735, Beijing 100080, People's Republic of China.
authors.forename: Shaojin
authors.initials: S
authors.lastname: Qin
authors.forename: Jizhong
authors.initials: J
authors.lastname: Lou
authors.forename: Liqun
authors.initials: L
authors.lastname: Sun
authors.forename: Changfeng
authors.initials: C
authors.lastname: Chen