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arXiv 1801.03052cond-mat.quant-gas
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双组分Bose-哈伯德模型中的超流阻力

Superfluid drag in the two-component Bose-Hubbard model

Karl Sellin, Egor Babaev

摘要:

在多组分超流体和超导体中,组分的共流和逆流通常具有不同的性质。1975年Andreev和Bashkin在He $^3$ /He $^4$超流体混合物的背景下讨论了粒子间相互作用产生无耗散阻力。阻力可以理解为一个组分的超流由另一个组分的相梯度引起。重要的是,阻力可以是正的(夹带)和负的(逆流)。这种效应对于不同物理系统的许多性质都至关重要,从中子星的动力学,超冷原子玻色混合物的旋转响应到多组分超导体的磁响应。虽然存在大量的文献,包括阻力相互作用的现象,少得多的制度所涵盖的定量研究的微观起源的阻力和其依赖于微观参数。本文研究了具有短程相互作用的格子上二分量玻色子量子系统中的拖曳相互作用的微观起源和强度。通过对两分量玻色-哈伯德模型进行量子蒙特卡罗模拟,得到了玻色-玻色相互作用和光晶格性质对拖曳强度的依赖关系。特别令人感兴趣的是强相关的制度,其中同向流和逆流超流刚度的比例可以发散,对应于饱和阻力的情况。

英文摘要:

In multicomponent superfluids and superconductors, co- and counter-flows of components have in general different properties. It was discussed in 1975 by Andreev and Bashkin, in the context of He$^3$/He$^4$ superfluid mixtures, that inter-particle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly the drag can be both positive (entrainment) and negative (counter-flow). The effect is known to be of crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars, rotational responses of Bose mixtures of ultra-cold atoms to magnetic responses of multicomponent superconductors. Although there exists a substantial literature that includes the drag interaction phenomenologically, much fewer regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte-Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly-correlated regimes where the ratio of co-flow and counter-flow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

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