title: Wannier permanent wave functions for featureless bosonic mott insulators on the 1/3-filled kagome lattice.
abstract: We study Bose-Hubbard models on tight-binding, non-Bravais lattices, with a filling of one boson per unit cell--and thus fractional site filling. We discuss situations where no classical bosonic insulator, which is a product state of particles on independent sites, is admitted. Nevertheless, we show that it is possible to construct a quantum Mott insulator of bosons if a trivial band insulator of fermions is possible at the same filling. The ground state wave function is simply a permanent of exponentially localized Wannier orbitals. Such a Wannier permanent wave function is featureless in that it respects all lattice symmetries and is the unique ground state of a parent Hamiltonian that we construct. Motivated by the recent experimental demonstration of a kagome optical lattice of bosons, we study this lattice at 1/3 site filling. Previous approaches to this problem have invariably produced either broken-symmetry states or topological order. Surprisingly, we demonstrate that a featureless insulator is a possible alternative and is the exact ground state of a local Hamiltonian. We briefly comment on the experimental relevance of our results to ultracold atoms as well as to 1/3 magnetization plateaus for kagome spin models in an applied field.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Parameswaran
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Itamar
authors.initials: I
authors.lastname: Kimchi
authors.affiliation: Institute for Theoretical Physics, University of Amsterdam, Science Park 904, P.O. Box 94485, 1090 GL Amsterdam, Netherlands.
authors.forename: Ari M
authors.initials: AM
authors.lastname: Turner
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Stamper-Kurn
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: Ashvin
authors.initials: A
authors.lastname: Vishwanath