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arXiv 0705.4198cond-mat.str-elcond-mat.supr-con
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公度密度下棋盘格点上扩展t-J模型的奇异Mott相

Exotic Mott phases of the extended t--J model on the checkerboard lattice at commensurate densities

Didier Poilblanc

摘要:

在简单的相称电子密度下,在受抑晶格上运动的电子之间的库仑排斥可以引起物质的奇异绝缘相。这种现象是使用一个扩展的t-J模型上的平面烧绿石晶格的四分之一填充的情况下[cond-mat/0702367]的工作是补充和扩展到1/8和3/8填充。的金属-绝缘体的过渡作为库仑排斥的函数的位置示出强烈依赖于跳跃的符号。通常,金属-绝缘体转变的特征在于晶格对称性破缺,但绝缘莫特态的性质比简单的电荷密度波更复杂。事实上,在大库仑排斥的限制下,物理学可以在(扩展的)量子完全填充环或二聚体模型的框架中描述,这些模型携带额外的自旋自由度。计算了各种对角和非对角元格关联函数,并详细分析了低能谱,以表征绝缘相的性质。我们提供的证据表明,对于n=1/2(四分之一填充)的电子密度,在$n=1/4$或$n=3/4$的系统也表现出元格秩序,通过形成(晶格旋转不变)共振单重对晶体,虽然与晶格晶胞的四倍(而不是加倍为$n=1/2$)和4倍简并基态。有趣的是,与玻色子类似物的定性差异(例如已知在n=1/4时表现出柱状有序)强调了自旋自由度在例如稳定格片相w.r.t.旋转对称性破缺相。

英文摘要:

Coulomb repulsion between electrons moving on a frustrated lattice can give rise, at simple commensurate electronic densities, to exotic insulating phases of matter. Such a phenomenon is illustrated using an extended t--J model on a planar pyrochlore lattice for which the work on the quarter-filled case [cond-mat/0702367] is complemented and extended to 1/8- and 3/8-fillings. The location of the metal-insulator transition as a function of the Coulomb repulsion is shown to depend strongly on the sign of the hopping. Quite generally, the metal-insulator transition is characterized by lattice symmetry breaking but the nature of the insulating Mott state is more complex than a simple Charge Density Wave. Indeed, in the limit of large Coulomb repulsion, the physics can be described in the framework of (extended) quantum fully-packed loop or dimer models carrying extra spin degrees of freedom. Various diagonal and off-diagonal plaquette correlation functions are computed and the low-energy spectra are analyzed in details in order to characterize the nature of the insulating phases. We provide evidence that, as for an electronic density of n=1/2 (quarter-filling), the system at $n=1/4$ or $n=3/4$ exhibits also plaquette order by forming a (lattice rotationally-invariant) Resonating-Singlet-Pair Crystal, although with a quadrupling of the lattice unit cell (instead of a doubling for $n=1/2$) and a 4-fold degenerate ground state. Interestingly, qualitative differences with the bosonic analog (e.g. known to exhibit columnar order at n=1/4) emphasize the important role of the spin degrees of freedom in e.g. stabilizing plaquette phases w.r.t. rotational symmetry-breaking phases.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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