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arXiv 1012.5943cond-mat.str-elcond-mat.mtrl-sci
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两粒子水平上强关联下Na $_x$ CoO $_2$中的竞争序

Competing orders in Na$_x$CoO$_2$ from strong correlations on a two-particle level

Lewin Boehnke, Frank Lechermann

摘要:

基于动态平均场论和连续时间量子Monte-Carlo杂质求解器,讨论了钴酸钠体系Na $_x$ CoO $_2$的静态和动态自旋电荷平衡相图。该方法包括重要的顶点贡献的q依赖的两粒子响应函数的局部近似的不可约的顶点函数的粒子孔通道。一个单带哈伯德模型足以揭示几个电荷和自旋不稳定性的趋势,根据实验,包括一个有效的kagome子晶格接近x=0.67的稳定,而不调用掺杂依赖的Na势景观。另外,通过计算的Korringa比验证了平面内反铁磁到铁磁交叉。此外,一个复杂的高能量模式中的横向自旋磁化率被揭示,指向一个强大的能量依赖性的有效intersite交换。

英文摘要:

Based on dynamical mean-field theory with a continuous-time quantum Monte-Carlo impurity solver, static as well as dynamic spin and charge susceptibilites for the phase diagram of the sodium cobaltate system Na$_x$CoO$_2$ are discussed. The approach includes important vertex contributions to the q-dependent two-particle response functions by means of a local approximation to the irreducible vertex function in the particle-hole channel. A single-band Hubbard model suffices to reveal several charge- and spin-instability tendencies in accordance with experiment, including the stabilization of an effective kagome sublattice close to x=0.67, without invoking the doping-dependent Na-potential landscape. The in-plane antiferromagnetic-to-ferromagnetic crossover is additionally verified by means of the computed Korringa ratio. Moreover an intricate high-energy mode in the transverse spin susceptiblity is revealed, pointing towards a strong energy dependence of the effective intersite exchange.

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