Structural transition, ferro-orbital order and its fluctuation-mediated -wave superconductivity in iron pnictides

详细信息	查看全文 | 推荐本文 |

• 作者：Yoshiaki Ō ; no^a ; ^b ; ^{y.ono@phys.sc.niigata-u.ac.jp} ; Yuki Yanagi^a ; Naoko Adachi^a ; Youichi Yamakawa^a
• 关键词：A. Superconductors ; D. Electron&ndash ; electron interactions ; D. Electron&ndash ; phonon interactions ; D. Phase transitions
• 刊名：Solid State Communications
• 出版年：2012
• 期刊代码：101_00381098
• 类别：ms
• 出版时间：April, 2012
• 卷：152
• 期：8
• 页码：701-710
• 文件大小：1124 K

摘要

We investigate the electronic states and the superconductivity in the two-dimensional 16-band - model extracted from a tight-binding fit to the band structure of iron pnictides, in the presence of both the Coulomb interaction between Fe -electrons and the electron-lattice coupling with the orthorhombic mode which is crucial for reproducing the recently observed ultrasonic softening of the elastic constant . Due to the cooperative effects of these interactions, the ferro-orbital order with different occupations of and orbitals occurs and induces the tetragonal-orthorhombic structural transition at , together with the stripe-type antiferromagnetic (AFM) order below . For a large case, we obtain the phase diagram consistent with the doped iron pnictides with for , where the -wave superconductivity is mediated by the ferro-orbital fluctuation which is largely enhanced near the ferro-orbital QCP at with . On the other hand, for a small case, the simultaneous phase transition occurs at even for , where the -wave superconductivity is mediated by the AFM fluctuation. Both the -wave states with full superconducting gaps are consistent with most of the experiments but only the former is considered to account for the small -suppression against nonmagnetic impurities.