title: Chiral magnetism and spontaneous spin Hall effect of interacting Bose superfluids.
abstract: Recent experiments on ultracold atoms in optical lattices have synthesized a variety of tunable bands with degenerate double-well structures in momentum space. Such degeneracies in the single-particle spectrum strongly enhance quantum fluctuations, and often lead to exotic many-body ground states. Here we consider weakly interacting spinor Bose gases in such bands, and discover a universal quantum 'order by disorder' phenomenon which selects a novel superfluid with chiral spin order displaying remarkable properties such as spontaneous spin Hall effect and momentum space antiferromagnetism. For bosons in the excited Dirac band of a hexagonal lattice, such a state supports staggered spin loop currents in real space. We show that Bloch oscillations provide a powerful dynamical route to quantum state preparation of such a chiral spin superfluid. Our predictions can be readily tested in spin-resolved time-of-flight experiments.
authors.affiliation: Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Li
authors.affiliation: Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors.forename: Stefan S
authors.initials: SS
authors.lastname: Natu
authors.affiliation: 1] Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7 [2] Canadian Institute for Advanced Research, Toronto, Ontario, Canada M5G 1Z8.
authors.forename: Arun
authors.initials: A
authors.lastname: Paramekanti
authors.affiliation: Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors.forename: S
authors.initials: S
authors.lastname: Das Sarma