Variant approaches, either based on the Fermi surface nesting or started from the proximity to a Mott-insulator, were proposed to elucidate the physics in iron pnictides, but no consensus has been reached. A fundamental problem concerns the nature of their 3d electrons. Here we report the magnetoresistivity (ρ_xx) and the Hall resistivity (ρ_xy) of Ba(Fe1-xCox)2As2 (x=0 and 0.05) in a magnetic field of up to 55T. The magnetic transition is extremely robust against magnetic field, giving strong evidence that the magnetic ordering is formed by local moments. The magnetic state is featured with a huge magnetoresistance and a distinguished Hall resistivity, ρ_xy(H), which shows a pronounced parabolic field dependence, while the paramagnetic state shows little magnetoresistance and follows a simple linear magnetic field dependence on the Hall resistivity. Analyses of our data, based on a two-carrier model, demonstrate that the electron carriers in the magnetic state rapidly increase upon applying a magnetic field, partially compensating the loss of electron carriers at T_M. We argue that the 3d-electrons in Ba(Fe1-xCox)2As2 are divided into those who are close to forming localized moments controlling the magnetic transition and the others giving rise to complex transport properties through their interaction with the former.
Successive magnetic transitions relating to itinerant spins and localized Cu spins in La2-xSrxCu1-yFeyO4: Possible existence of stripe correlations in the overdoped regime
为了研究所谓的条纹关联与高温超导性之间的关系，我们对部分Fe取代的La 2-xSrxCu 1-yFeyO 4（LSCFO）进行了磁化率和零场μ子自旋弛豫测量.已经发现，Fe替代诱导连续的磁过渡在过掺杂制度，即，由于RKKY相互作用的基础上巡回自旋在较高的温度和条纹顺序过渡的本地化的Cu 2+自旋在较低的温度下的Fe 3+自旋的自旋玻璃化转变。条纹顺序过渡消失的空穴浓度约0.28每铜，这与在原始的La 2-xSrxCuO 4的超导性的终点相吻合，表明条纹的相关性是密切相关的高Tc超导电性在过掺杂制度，以及在欠掺杂制度。对于自旋玻璃态，我们发现极化巡游自旋对μ子自旋去极化的贡献是不可忽略的。考虑到R.- H. He等人[Phys. Rev. Lett. 107，127002（2011）]，已经在过掺杂的LSCFO中观察到自旋密度波（SDW）序，本结果证明了SDW序和自旋玻璃态的新共存态的存在。
Coexistence of localized and itinerant magnetism in newly discovered iron-selenide superconductor LiFeO2Fe2Se2
采用第一性原理方法研究了LiFeO $_{2}$ Fe $_{2}$ Se $_{2}$的电子结构和磁性.在LiFeO $_{2}$层中，Fe 1的基态为N $\acute{e}$ el反铁磁（AFM）Mott绝缘态，具有局域磁性;在Fe $_{2}$ Se $_{2}$层中，Fe 2的基态为条纹状AFM金属态，具有巡游磁性;此外，层状LiFeO $_{2}$被发现是超过一个绝缘块层，但负责增强AFM相关的Fe $_{2}$ Se $_{2}$层通过层间磁耦合。Fe 1和Fe 2的磁性之间的相互作用引入了与铁基超导体中的超导性相关的自旋涨落的控制机制。
Spin fluctuations and pairing symmetry in A$_{x}$Fe$_{2-y}$Se$_{2}$: dual effect of the itinerant and the localized nature of electrons
在涨落交换近似下，研究了A $_{x}$ Fe $_{2-y}$ Se $_{2}$中的自旋涨落和对对称性.除了在位相互作用外，还考虑了次近邻反铁磁耦合$J_{2}$。我们发现电子的巡游性质和局域性质对描述最近的自旋涨落和对对称性的实验结果都很重要。特别地，小的$J_{2}$耦合可以将配对间隙从d波对称改变为s波对称。我们还研究了不同轨道的间隙函数的实空间结构，以便更深入地了解配对机制的性质。
Two-electronic component behavior in the multiband FeSe$_{0.42}$Te$_{0.58}$ superconductor
本文报道了单晶超导FeSe $_{0.42}$ Te $_{0.58}$（$T_c$ = 11.5（1）K）的X波段EPR和$^{125}$ Te和$^{77}$ Se NMR测量结果。这些数据提供了证据的共存的内在本地化和巡回电子状态。在正常状态下，局域磁矩耦合到Fe（Se，Te）层中的巡游电子，并影响局域自旋磁化率和自旋涨落。在$T_c$以下，自旋涨落被迅速抑制，出现了一种非常规的超导状态，其中$1/T_1$以比传统的$s$或$s_\pm$波对称所预期的快得多的速率被还原。我们认为，局域态产生的强电子相关内的Fe衍生带。多带电子结构与电子相关性一起决定了FeSe $_{1-x}$ Te $_x$族的正常态和超导态，它似乎比以前预期的更接近其他高$T_c$超导体。
Hidden itinerant-spin phase in heavily-overdoped La2-xSrxCuO4 revealed by dilute Fe doping: A combined neutron scattering and angle-resolved photoemission study
The dual nature of magnetism in a uranium heavy fermion system
在$5\textit{f}$电子系统中，磁性的定域性和巡游性之间的二元性一直是一个长期存在的难题。在这里，我们报告的非弹性中子散射测量，这揭示了本地和巡回方面的磁性在一个单晶系统的UPt $_{2}$ Si $_{2}$。在反铁磁状态下，我们观察到广泛的连续的扩散磁散射与$\approx$ 7 meV的共振间隙，并令人惊讶的相干自旋波的情况下，巡回磁性的暗示。当Neel温度以上的间隙关闭时，强的动态自旋相关持续到高温。然而，总磁谱权重的大小和温度依赖性可以很好地描述与$J=4$的本地矩。此外，极化中子测量显示，磁波动主要是横向的，很少或根本没有预期的巡游时刻的纵向分量。这些结果表明，本地和巡回磁性的双重描述，需要了解UPt $_{2}$ Si $_{2}$，并通过扩展，其他5 $f$系统一般。
Orbital-Selective $d$-wave Superconductivity in the Two-Band $t$-$J$ Model: Possible Applications to La$_3$Ni$_2$O$_7$
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；School of Physical Science and Technology, ShanghaiTech University（上海科技大学物理科学与技术学院）；Kavli Institute for Theoretical Sciences and School of Quantum, University of Chinese Academy of Sciences（中国科学院大学量子科学与量子技术学院）
