Jian Yue, Zhang Ai-Xia, He Cai-Xia, Qi Xiu-Ying, Xue Ju-Kui
College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 May;87(5):053201. doi: 10.1103/PhysRevE.87.053201. Epub 2013 May 28.
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.
我们研究了由非局部非线性离散格罗斯 - 皮塔耶夫斯基方程描述的深晶格中偶极气体的动力学。详细讨论了具有缺陷的系统中行波平面波的稳定性和传播特性。对于无缺陷晶格，研究了行波平面波的能量稳定性和动力学稳定性。结果表明，具有吸引性局部相互作用的系统可以保持稳定性，即由于排斥性非局部偶极 - 偶极相互作用，偶极子可以使气体稳定。对于有缺陷的晶格，在双模近似下，系统中行波平面波的传播特性映射到具有依赖于准动量的非线性（由非局部相互作用引起）的非刚性摆哈密顿量上。缺陷、气体的准动量和非局部相互作用之间的竞争决定了行波平面波的传播特性。通过解析得到并通过数值验证了从传播得以保持的超流态转变为具有缺陷诱导阻尼的正常态的临界条件。特别地，支持超流性的临界条件强烈依赖于缺陷类型和平面波的准动量。非局部相互作用可以显著增强系统的超流性。
