title: Microscopic realization of two-dimensional bosonic topological insulators.
abstract: It is well known that a bosonic Mott insulator can be realized by condensing vortices of a boson condensate. Usually, a vortex becomes an antivortex (and vice versa) under time reversal symmetry, and the condensation of vortices results in a trivial Mott insulator. However, if each vortex or antivortex interacts with a spin trapped at its core, the time reversal transformation of the composite vortex operator will contain an extra minus sign. It turns out that such a composite vortex condensed state is a bosonic topological insulator (BTI) with gapless boundary excitations protected by U(1)⋊Z2(T) symmetry. We point out that in BTI, an external π-flux monodromy defect carries a Kramers doublet. We propose lattice model Hamiltonians to realize the BTI phase, which might be implemented in cold atom systems or spin-1 solid state systems.
authors.affiliation: Institute for Advanced Study, Tsinghua University, Beijing 100084, People's Republic of China and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 Canada.
authors.forename: Zheng-Xin
authors.initials: ZX
authors.lastname: Liu
authors.affiliation: Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 Canada.
authors.forename: Zheng-Cheng
authors.initials: ZC
authors.lastname: Gu
authors.affiliation: Institute for Advanced Study, Tsinghua University, Beijing 100084, People's Republic of China and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 Canada and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Xiao-Gang
authors.initials: XG
authors.lastname: Wen