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arXiv 0905.0382cond-mat.supr-con
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具有共线反铁磁芯的铁基超导体中的涡旋态

Vortex state in iron-based superconductors with collinear antiferromagnetic cores

Hong-Min Jiang, Jian-Xin Li, Z. D. Wang

摘要:

通过自洽求解基于双轨道模型的BdG方程,考虑了两个轨道上电子之间的在位相互作用,研究了FeAs化学计量比化合物的磁性及其与涡旋态超导性的相互作用.结果表明,对于母体化合物,磁性是由强的Hund耦合引起的,费米表面拓扑有助于选择自旋密度波(SDW)模式。结果表明,具有$s_{\pm}=Δ_{0}\cos(k_{x})\cos(k_{y})$对称性的超导序参量对电子掺杂和空穴掺杂都是最有利的配对,而局域态密度(LDOS)对电子掺杂和空穴掺杂都表现出节隙和全隙的特征.在涡旋态,场致SDW的出现取决于Hund耦合和库仑排斥的强度。场致SDW间隙的电子和空穴袋侧的有限能量轮廓,导致与一个反映SC配对和其他相关的SDW顺序的双重结构。这些特征可以在STM测量中辨别,用于识别场诱导的SDW阶和核心区域周围的SC阶之间的相互作用。

英文摘要:

Magnetism in the FeAs stoichiometric compounds and its interplay with superconductivity in vortex states are studied by self-consistently solving the BdG equations based on a two-orbital model with including the on-site interactions between electrons in the two orbitals. It is revealed that for the parent compound, magnetism is caused by the strong Hund's coupling, and the Fermi surface topology aids to select the spin-density-wave (SDW) pattern. The superconducting (SC) order parameter with $s_{\pm}=Δ_{0}\cos(k_{x})\cos(k_{y})$ symmetry is found to be the most favorable pairing for both the electron- and hole-doped cases, while the local density-of-states (LDOS) exhibits the characteristic of nodal gap for the former and full gap for the latter. In the vortex state, the emergence of the field-induced SDW depends on the strength of the Hund's coupling and the Coulomb repulsions. The field-induced SDW gaps the finite energy contours on the electron and hole pocket sides, leading to the dual structures with one reflecting the SC pairing and the other being related to the SDW order. These features can be discernable in STM measurements for identifying the interplay between the field-induced SDW order and the SC order around the core region.

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