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arXiv 1006.3535cond-mat.supr-con
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基于涨落键模型的铜氧化物高温超导体赝能隙的从头算研究

Ab initio Understanding of the Pseudogap in Cuprate High Temperature Superconductors via the Fluctuating Bond Model

R. A. Nistor, G. J. Martyna, D. M. Newns, C. C. Tsuei, M. H. Mueser

摘要:

理解赝能隙的起源是阐明铜氧化物超导体中的配对机制的重要一步。最近有强有力的实验证据表明,C4对称性破缺发生在赝能隙的形成。这种形式的对称性破缺是由波动键模型(FBM)预测的,波动键模型是一种基于电子与平面氧振子振幅平方的强局部耦合的经验模型。在本文中,我们从一个新的方向,从{ \it ab initio}分子动力学模拟开始的FBM理论。模拟结果表明,掺杂依赖的不稳定性的面内氧对位移的Cu-O-Cu键轴。根据这些结果和微扰理论,我们导出了涨落键模型的一个改进的定量形式。FBM的平均场解导致氧振动振幅的C4对称性破缺,以及电子光谱中的d型赝能隙,这些特征与最近的实验数据有关。从平均场论推导出的赝能隙的相图,其掺杂和温度依赖性,包括相边界T $^*$,符合实验数据。我们扩展的理论,包括长程库仑相互作用的FBM相互作用的基础上。当长程库仑相互作用包括在FBM中,电荷通道中的CDW不稳定性的预测,这解释了纳米级,而不是空间均匀的,行为的C4的库仑断裂。考虑到CDW,与理论上的k依赖性的赝隙,使费米表面弧现象得到理解。

英文摘要:

Understanding the origin of the pseudogap is an essential step towards elucidating the pairing mechanism in the cuprate superconductors. Recently there has been strong experimental evidence showing that C4 symmetry breaking occurs on formation of the pseudogap. This form of symmetry breaking was predicted by the Fluctuating Bond Model (FBM), an empirical model based on a strong, local coupling of electrons to the square of the planar oxygen vibrator amplitudes. In this paper we approach the FBM theory from a new direction, starting from {\it ab initio} molecular dynamics simulations. The simulations demonstrate a doping-dependent instability of the in-plane oxygens towards displacement off the Cu-O-Cu bond axis. From these results and perturbation theory we derive an improved and quantitative form of the Fluctuating Bond Model. A mean field solution of the FBM leads to C4 symmetry breaking in the oxygen vibrational amplitudes, and to a d-type pseudogap in the electronic spectrum, the features linked by recent experimental data. The phase diagram of the pseudogap derived from mean field theory, its doping- and temperature-dependences, including the phase boundary T$^*$, agree well with experimental data. We extend the theory to include the long range Coulomb interaction on the same basis as the FBM interaction. When the long-range Coulomb interaction is included in the FBM, a CDW instability in the charge channel is predicted which explains the nanoscale, rather than spatially uniform, behavior of the C4 symmetry-breaking. Taking the CDW into account, with the theoretical k-dependence of the pseudogap, enables the Fermi Surface arc phenomenon to be understood.

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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