Vortex core states in a minimal two-band model for iron-based superconductors
Vortex core states in a minimal two-band model for iron-based superconductors
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DOI：
10.1103/physrevb.80.014523
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发表时间：
2009-05
期刊：
影响因子：
--
通讯作者：
Xiang Hu;C. Ting;Jian-Xin Zhu
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文献类型：
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作者：
Xiang Hu;C. Ting;Jian-Xin Zhu
配对对称性是铁基超导体研究的主要问题之一。我们采用具有各种配对相互作用通道的最小二能带紧束缚模型，并推导了一组二能带 Bogoliubov-de Gennes (BdG) 方程。 BdG 方程在实空间中实现，然后通过精确对角化自洽求解。在统一情况下，我们发现 $d_{x^2-y^2}$ 波配对状态最有利于最近邻配对交互，而 $s_{x^2y^2}$ 波配对状态最有利于次近邻配对交互。这与 Seo {\em 等人} [Phys.莱特牧师。 {\bf 101}，206404（2008）]。然后，我们继续研究混合状态下 $d_{x^2-y^2}$ 波和 $s_{x^2y^2}$ 波配对对称性磁涡核周围的局域电子结构。从局域态密度(LDOS)谱及其空间变化发现，$d_{x^2-y^2}$波配对对称性的费米能附近的共振核心态是束缚的，而$s_{x^2y^2}$波配对对称性的共振核心态可以从局域态演化为具有不同电子填充因子的扩展态。此外，通过包含有效的交换相互作用，新兴的反铁磁自旋密度波（SDW）阶可以抑制共振核心态，这为理解共振峰的缺失提供了一种可能的途径，正如 Yin 等人最近的扫描隧道显微镜实验（STM）所揭示的那样。莱特牧师。 {\bf 102}，097002（2009）]。
The pairing symmetry is one of the major issues in the study of iron-based superconductors. We adopt a minimal two-band tight-binding model with various channels of pairing interaction, and derive a set of two-band Bogoliubov-de Gennes (BdG) equations. The BdG equations are implemented in real space and then solved self-consistently via exact diagonalization. In the uniform case, we find that the $d_{x^2-y^2}$-wave pairing state is most favorable for a nearest-neighbor pairing interaction while the $s_{x^2y^2}$-wave pairing state is most favorable for a next-nearest-neighbor pairing interaction. The is consistent with that reported by Seo {\em et al.} [Phys. Rev. Lett. {\bf 101}, 206404 (2008)]. We then proceed to study the local electronic structure around a magnetic vortex core for both $d_{x^2-y^2}$-wave and $s_{x^2y^2}$-wave pairing symmetry in the mixed state. It is found from the local density of states (LDOS) spectra and its spatial variation that the resonance core states near the Fermi energy for the $d_{x^2-y^2}$-wave pairing symmetry are bound while those for the $s_{x^2y^2}$-wave pairing symmetry can evolve from the localized states into extended ones with varying electron filling factor. Furthermore, by including an effective exchange interaction, the emergent antiferromagnetic spin-density-wave (SDW) order can suppress the resonance core states, which provides one possible avenue to understand the absence of resonance peak as revealed by recent scanning tunneling microscopy experiment (STM) by Yin {\em et al.} [Phys. Rev. Lett. {\bf 102}, 097002 (2009)].