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arXiv 1305.2995cond-mat.supr-concond-mat.str-el
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铁基超导体中电子-声子相互作用对轨道涨落的影响

Effect of electron-phonon interactions on orbital fluctuations in iron-based superconductors

Yusuke Nomura, Kazuma Nakamura, Ryotaro Arita

摘要:

为了研究铁基超导体中电子-声子耦合是否会增强轨道涨落,我们发展了一种从头算方法来构建包含声子相关项的有效低能模型.利用导出的有效电子-声子相互作用和声子频率,我们估计声子介导的有效在位轨道内或轨道间电子-电子吸引的静态部分(ω=0)为~ -0.4 eV,交换或对跳跃项为~ -0.02 eV。我们分析了模型与衍生的相互作用与电子排斥内的随机相位近似。我们发现,由于电子-声子相互作用的轨道涨落的增强是小的,使自旋涨落占主导地位。结果,实现了带隙函数符号反转的超导态($s_\pm$波)。

英文摘要:

To investigate the possibility whether electron-phonon coupling can enhance orbital fluctuations in iron-based superconductors, we develop an ab initio method to construct the effective low-energy models including the phonon-related terms. With the derived effective electron-phonon interactions and phonon frequencies, we estimate the static part (ω=0) of the phonon-mediated effective on-site intra- or inter-orbital electron-electron attractions as ~ -0.4 eV and exchange or pair-hopping terms as ~ -0.02 eV. We analyze the model with the derived interactions together with the electronic repulsions within the random phase approximation. We find that the enhancement of the orbital fluctuations due to the electron-phonon interactions is small, making the spin fluctuations dominant. As a result, the superconducting state with the sign reversal in gap functions ($s_\pm$-wave) is realized.

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