title: Counterflow superfluidity of two-species ultracold atoms in a commensurate optical lattice.
abstract: In the Mott-insulator regime, two species of ultracold atoms in an optical lattice can exhibit the low-energy counterflow motion. We construct effective Hamiltonians for the three classes of the two-species (fermion-fermion, boson-boson, and boson-fermion-type) insulators and reveal the conditions when the resulting ground state supports super-counter-fluidity (SCF), with the alternative being phase segregation. We emphasize a crucial role of breaking the isotopic symmetry between the species for realizing the SCF phase.
authors.affiliation: The College of Staten Island, CUNY, Staten Island, New York 10314, USA.
authors.forename: A B
authors.initials: AB
authors.lastname: Kuklov
authors.forename: B V
authors.initials: BV
authors.lastname: Svistunov