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arXiv 1007.0400cond-mat.str-elcond-mat.dis-nn
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空间不均匀性对强相互作用费米子与弱相互作用自旋映射的影响

Effect of spatial inhomogeneity on the mapping between strongly interacting fermions and weakly interacting spins

Vivian V. França, Klaus Capelle

摘要:

在Hubbard、t-J和Heisenberg模型的框架下,对强相互作用费米子和弱相互作用自旋之间的映射进行了分析和数值研究.虽然在热力学极限的空间均匀模型的映射是彻底理解,我们在这里专注于在空间不均匀的情况下,如边界,杂质,超晶格和界面的影响成为相关的方面。我们认为这些模型的传统应用,如铜酸盐和锰氧化物中的电子,以及最近的应用程序在光晶格中的原子的参数制度。作为相互作用强度的函数的映射的速率由无限系统的Bethe-Anglomeration和有限系统的数值对角化确定。我们分析表明,如果平移对称性被打破,通过杂质的存在下,映射仍然存在,并在一定意义上,尽可能本地,提供的两个站点之间的海森堡模型的自旋-自旋相互作用是从现场库仑相互作用的谐波平均值计算相邻站点的哈伯德模型。数值计算也证实了这些发现在界面和超晶格,在那里分析计算更复杂。

英文摘要:

A combined analytical and numerical study is performed of the mapping between strongly interacting fermions and weakly interacting spins, in the framework of the Hubbard, t-J and Heisenberg models. While for spatially homogeneous models in the thermodynamic limit the mapping is thoroughly understood, we here focus on aspects that become relevant in spatially inhomogeneous situations, such as the effect of boundaries, impurities, superlattices and interfaces. We consider parameter regimes that are relevant for traditional applications of these models, such as electrons in cuprates and manganites, and for more recent applications to atoms in optical lattices. The rate of the mapping as a function of the interaction strength is determined from the Bethe-Ansatz for infinite systems and from numerical diagonalization for finite systems. We show analytically that if translational symmetry is broken through the presence of impurities, the mapping persists and is, in a certain sense, as local as possible, provided the spin-spin interaction between two sites of the Heisenberg model is calculated from the harmonic mean of the onsite Coulomb interaction on adjacent sites of the Hubbard model. Numerical calculations corroborate these findings also in interfaces and superlattices, where analytical calculations are more complicated.

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