title: Dynamics of a nonlocal discrete Gross-Pitaevskii equation with defects.
abstract: We study the dynamics of dipolar gas in deep lattices described by a nonlocal nonlinear discrete Gross-Pitaevskii equation. The stabilities and the propagation properties of traveling plane waves in the system with defects are discussed in detail. For a clean lattice, both energetic and dynamical stabilities of the traveling plane waves are studied. It is shown that the system with attractive local interaction can preserve the stabilities, i.e., the dipoles can stabilize the gas because of repulsive nonlocal dipole-dipole interactions. For a lattice with defects, within a two-mode approximation, the propagation properties of traveling plane waves in the system map onto a nonrigid pendulum Hamiltonian with quasimomentum-dependent nonlinearity (induced by the nonlocal interactions). Competition between defects, quasimomentum of the gas, and nonlocal interactions determines the propagation properties of the traveling plane waves. Critical conditions for crossing from a superfluid regime with propagation preserved to a normal regime with defect-induced damping are obtained analytically and confirmed numerically. In particular, the critical conditions for supporting the superfluidity strongly depend on the defect type and the quasimomentum of the plane waves. The nonlocal interaction can significantly enhance the superfluidity of the system.
authors.affiliation: College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Jian
authors.forename: Ai-Xia
authors.initials: AX
authors.lastname: Zhang
authors.forename: Cai-Xia
authors.initials: CX
authors.lastname: He
authors.forename: Xiu-Ying
authors.initials: XY
authors.lastname: Qi
authors.forename: Ju-Kui
authors.initials: JK
authors.lastname: Xue
mesh_terms: D003198:Computer Simulation; D005740:Gases / Q000737:chemistry*; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D017711:Nonlinear Dynamics
chemical_list: D005740:Gases