采用二阶微扰格林函数方法，我们确定了正常状态的单粒子光谱函数$A(\vec{k},ω)$采用最小有效模型的铁基超导体。以前用于研究磁涨落和超导性质的微观模型包括S.Raghu等人提出的两个有效紧束缚带[Phys. Rev. B 77，220503（R）（2008）]，以及与Fe-3d轨道相关的轨道内和轨道间局部电子相关性。在这里，我们专注于正常状态的电子性质的研究，特别是温度和掺杂的总态密度，$A(ω)$，和$A(\vec{k},ω)$在不同的布里渊区区域的依赖关系，并将它们与现有的角度分辨光电子能谱（ARPES）和以前的理论结果在铁磷族化合物。我们得到的电子和空穴掺杂的非对称效应，定量协议与实验的化学势作为掺杂的函数，以及光谱重量重新分布附近的费米能级作为温度的函数与现有的实验数据一致。此外，我们预测了一个非平凡的总态密度与温度的依赖关系，表现出明确的重整化效应的相关性。有趣的是，通过分析在我们的方法中获得的依赖于k的自能随温度的演化来研究这种预测行为的起源，我们可以确定一些特定的布里渊区点，其中没有一个被ARPES实验探测到，其中存在温度对重整化的最大非平凡影响。
英文摘要：
Using a second-order perturbative Green's functions approach we determined the normal state single-particle spectral function $A(\vec{k},ω)$ employing a minimal effective model for iron-based superconductors. The microscopic model, used before to study magnetic fluctuations and superconducting properties, includes the two effective tight-binding bands proposed by S.Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and intra- and inter-orbital local electronic correlations, related to the Fe-3d orbitals. Here, we focus on the study of normal state electronic properties, in particular the temperature and doping dependence of the total density of states, $A(ω)$, and of $A(\vec{k},ω)$ in different Brillouin zone regions, and compare them to the existing angle resolved photoemission spectroscopy (ARPES) and previous theoretical results in ferropnictides. We obtain an asymmetric effect of electron and hole doping, quantitative agreement with the experimental chemical potential shifts as a function of doping, as well as spectral weight redistributions near the Fermi level as a function of temperature consistent with the available experimental data. In addition, we predict a non-trivial dependence of the total density of states with the temperature, exhibiting clear renormalization effects by correlations. Interestingly, investigating the origin of this predicted behaviour by analyzing the evolution with temperature of the k-dependent self-energy obtained in our approach, we could identify a number of specific Brillouin zone points, none of them probed by ARPES experiments yet, where the largest non-trivial effects of temperature on the renormalization are present.
Symmetry of spin excitation spectra in the tetragonal paramagnetic and superconducting phases of 122-ferropnictides
通过比较第一性原理计算和非弹性中子散射（INS）测量结果，研究了122-铁磷族化合物超导体中既没有静态磁相也没有结构相变的BaFe 1.85 Co 0.15 As 2和BaFe 1.91 Ni 0.09 As 2样品的自旋激发谱的对称性.在正常和超导（SC）状态下，光谱缺乏围绕（1/2 1/2 L）轴的42/m螺旋对称性，这是由I4/mmm空间群所暗示的。这在正常和SC状态自旋动力学的面内各向异性和自旋共振模式的面外色散中都是明显的。我们发现，这种效果源于较高的对称性的磁性Fe子晶格相对于晶体本身，因此INS信号继承了对称性的展开布里渊区（BZ）的Fe子晶格。面内各向异性是温度无关的，并且可以在正常状态密度泛函理论计算中定性地再现，而不调用先前提出的作为对这种效应的解释的破缺（“破缺”）基态。在SC转变之下，磁共振模式Er的能量以及其强度和SC自旋间隙继承了沿着面外方向L的正常态强度调制，其周期比体心四面体BZ对称性所预期的大两倍。这种调制的幅度在更高的掺杂降低，提供了一个类比，在双层铜酸盐的偶和奇谐振模式之间的分裂。结合我们和以前的数据，我们表明，在奇数L的一个普遍的线性关系Er=4.3*kB*Tc持有所有研究的铁基超导体，独立于他们的载体类型。它的有效性下降到最低的掺杂水平是一致的，与较弱的电子相关性在铁磷族化合物相比，欠掺杂的铜酸盐。
We report an angle-resolved photoemission study of a series of hole and electron doped iron-based superconductors, their parent compound BaFe2As2, and their cousins BaCr2As2 and BaCo2As2. We focus on the energy (E) dependent scattering rate Gamma(E) as a function of the 3d count and on the renormalization function Z(E) of the inner hole pocket, which is the hot spot in these compounds. We obtain a non-Fermi-liquid-like linear in energy scattering rate Gamma(E>> kBT), independent of the dopant concentration. The main result is that the slope beta=Gamma(E >> kBT)/E, reaches its maxima near optim…
Orbital character variation of the Fermi surface and doping dependent changes of the dimensionality in BaFe2-xCoxAs2 from angle-resolved photoemission spectroscopy
The pairing glue of high-$T_{\rm c}$ superconductivity in heavily electron-doped (e-doped) FeSe, in which hole-pockets are absent, has been an important unsolved problem. Here, we focus on a heavily e-doped bulk superconductor Li$_{1-x}$Fe$_x$OHFeSe ($T_{\rm c} \sim 40$K). We construct a multiorbital model beyond the rigid band approximation and analyze the spin and orbital fluctuations by taking both vertex corrections (VCs) and self-energy into consideration. Without e-doping ($x=0$), the ferro-orbital order without magnetism in FeSe is reproduced by the VCs.The orbital order quickly disappe…
The recent discovery of superconductivity in Nd$_{1-x}$Sr$_{x}$NiO$_2$ has drawn significant attention in the field. A key open question regards the evolution of the electronic structure with respect to hole doping. Here, we exploit x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) to probe the doping dependent electronic structure of the NiO$_2$ planes. Upon doping, a higher energy feature in Ni $L_3$ edge XAS develops in addition to the main absorption peak. By comparing our data to atomic multiplet calculations including $D_{4h}$ crystal field, the doping in…
Orbital-selective electronic modes induced by doping and originating from distinct spin excitations: an essential feature of orbital-selective Mott transition
Research Center for Materials Nanoarchitectonics, National Institute for Materials Science（物质纳米结构研究中心，日本国立物质材料研究所）
Effect of doping on the electronic structure, orbital-dependent renormalizations, and magnetic correlations in bilayer La$_3$Ni$_2$O$_7$
M. N. Mikheev Institute of Metal Physics, Russian Academy of Sciences（俄罗斯科学院 M.N. 米凯耶夫金属物理研究所）；Institute of Physics and Technology, Ural Federal University（乌拉尔联邦大学物理与技术研究所）
Topological Chiral Superconductivity from Doping Correlated Charge Transfer Insulator with Orbital Magnetism
Great Bay Institute for Advanced Study, Great Bay University（大湾区先进科技学院）；Great Bay University（大湾区大学）；Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China（中国科学院微观尺度物理科学国家研究中心及中国科学技术大学物理科学学院）
The recent detailed study of quasi-one-dimensional iron-based ladders, with the $3d$ iron electronic density $n = 6$, has unveiled surprises, such as orbital-selective phases. However, similar studies for $n=6$ iron chains are still rare. Here, a three-orbital electronic Hubbard model was constructed to study the magnetic and electronic properties of the quasi-one-dimensional $n=6$ iron chain Ce$_2$O$_2$FeSe$_2$, with focus on the effect of doping. Specifically, introducing the Hubbard $U$ and Hund $J_{H}$ couplings and studying the model via the density matrix renormalization group, we report…
Localization and Orbital Selectivity in Iron-Based Superconductors with Cu Substitution
利用扩展的实空间格林函数方法结合密度泛函计算，研究了Cu取代铁磷属元素化合物的非均匀三轨道哈伯德模型.我们发现，现场的相互作用的Cu离子是电子掺杂剂或空穴掺杂剂是由Cu取代的主要决定因素。结果表明，Cu离子的相互作用小于某一临界值时，Cu离子的取代将导致空穴掺杂，而Cu离子的相互作用大于某一临界值时，Cu离子的取代将导致电子掺杂，这可以解释为什么Cu取代对NaFe $_{1-x}$ Cu $_x$ As和Ba（Fe $_{1-x}$ Cu $_x$）$_2$ As $_2$载流子密度的影响是完全不同的.我们还发现掺杂诱导的无序效应在Cu取代的铁磷属元素化物中是相当可观的，并且它与电子关联的协同效应有助于NaFe $_{1-x}$ Cu $_x$ As和Ba（Fe $_{1-x}$ Cu $_x$）$_2$ As $_2$中的轨道选择绝缘相。
We investigate the electronic structure of nickelate superconductor NdNiO2 upon hole doping, by means of density-functional theory and dynamical mean-field theory. We demonstrate the strong intrinsic hybridization between strongly correlated states formed by Ni-3dx2-y2 orbital and itinerant electrons due to Nd-5d and Ni-3dz2 orbitals, producing a valence-fluctuating correlated metal as the normal state of hole-doped NdNiO2. The Hund's rule appears to play a dominating role on multi-orbital physics in the lightly doped compound, while its effect is gradually reduced by increasing the doping lev…
Variational Monte Carlo study of a two-orbital Hubbard model for the iron pnictides
International School for Advanced Studies (SISSA) and CNR-IOM（国际高等研究院（SISSA）与意大利国家研究委员会凝聚态物理研究所（CNR-IOM））；Institute for Condensed Matter Physics and Complex Systems, DISAT, Politecnico di Torino（都灵理工大学DISAT凝聚态物理与复杂系统研究所）
Origin of doping-induced suppression and reemergence of magnetism in LaFeAsO$_{1-x}$H$_x$
利用动力学平均场理论结合密度泛函理论研究了铁基超导体LaFeAsO $_{1-x}$ H $_x$中氢掺杂对磁性的影响.我们发现，两个独立的结果的掺杂，电子占据和结构修改的增加，有相反的影响的电子相关性和磁性的强度，导致在中间掺杂水平附近的计算磁矩的最小值作为$x$的函数。我们的结果提供了一个自然的解释，令人费解的最近实验发现的两个分离的反铁磁相在低和高掺杂限制。此外，随着掺杂量的增加，轨道占有率和关联强度的增加，导致$d_{xz/yz}$轨道极化率的降低和$d_{xy}$轨道在磁性中的作用的增强，并结合磁性的本质作用讨论了它们对超导性的可能影响.
Charge-doping-induced variation of BaFe$_2$As$_2$ electronic structure and the emerging physical effects
在密度泛函理论结合动力学平均场论（DFT+DMFT）的框架下，研究了BaFe $_2$ As $_2$化合物的电荷掺杂与关联的关系及其对光谱函数的影响.计算的质量增强表明，电子关联从弱到强系统地变化时，从重电子掺杂的制度，重空穴掺杂的。由于该化合物具有多轨道性质，相关性是轨道依赖性的，并且随着空穴掺杂的增加而增加。Fe-3d $_{xy}$（xy）轨道的相关性比其他轨道大得多，因为它达到了半满状态，并且在费米能附近具有更窄的能量标度。我们的研究结果可以一致地理解为重空穴掺杂的BaFe $_2$ As $_2$化合物的轨道选择性莫特相（OSMP）的趋势。此外，重空穴掺杂BaFe $_2$ As $_2$的超导态是这种选择性Mottness的极端情况，这一事实限制了铁磷属元素化物超导体中电子相关的重要作用。此外，计算的光谱函数显示的行为，是兼容的实验结果报告的每一个电荷掺杂的BaFe $_2$作为$_2$化合物，并澄清其物理效应的表征的重要性的材料。
Substitutional doping of Cu in diamond: Mott physics with $p$ orbitals
在金刚石中重掺硼（C：B）和硅中重掺硼（Si：B）形成的杂质带中发现超导性，为新的超导材料族的可能性提供了一条途径。基于铜原子在高温超导材料中所起的特殊作用，本文研究了铜原子在金刚石中的替代掺杂效应。在高温超导材料中，铜原子的$d$轨道是产生各种关联诱导相的主要原因。我们广泛的第一性原理计算平均在各种几何形状的基础上密度泛函理论，表明形成的中间带隙，这主要是由于$t_{2g}$和$4p$状态的铜。当杂质浓度大于$\sim 1%, the effect of $ 2 p $ bands of neighboring carbon atoms can be ignored. Based on our detailed analysis, we suggest a two band model for the mid-gap states consisting of a quarter-filled hole like $ t_{2g} $ band, and a half-filled band of $ 4 p $ states. Increasing the concentration of the Cu impurity beyond $ \sim 5%时，完全关闭基质金刚石的光谱间隙。
Evolution of magneto-orbital order upon B-site electron doping in Na1-xCaxMn7O12 quadruple perovskite manganites
我们提出了一个新的磁性相在Na 1-xCaxMn 7 O 12四重钙钛矿相图，这是众所周知的伪CE相的简单的钙钛矿锰氧化物的无公度的类似物的中子粉末衍射的发现和细化。我们证明了在四重钙钛矿中由于A和B位点之间的交换相互作用而产生的无公度磁序。此外，通过构建一个简单的平均场海森堡交换模型，一般描述简单和四重钙钛矿系统，我们表明，这种新的磁性相统一的图片之间的相互作用的电荷，磁性和轨道之间的排序在广泛的化合物。
We review the electronic structure of nickelate superconductors with and without effects of electronic correlations. As a minimal model we identify the one-band Hubbard model for the Ni 3$d_{x^2-y^2}$ orbital plus a pocket around the $A$-momentum. The latter however merely acts as a decoupled electron reservoir. This reservoir makes a careful translation from {nominal} Sr-doping to the doping of the one-band Hubbard model mandatory. Our dynamical mean-field theory calculations, in part already supported by experiment, indicate that the $Γ$ pocket, Nd 4$f$ orbitals, oxygen 2$p$ and {the} other …
The recent observation of superconductivity in infinite-layer nickelates has brought intense debate on the established knowledge of unconventional superconductivity based on the cuprates. Despite many similarities, the nickelates differ from the cuprates in many characteristics, the most notable one among which is the magnetism. Instead of a canonical antiferromagnetic Mott insulator as the undoped cuprates, from which the superconductivity is generally believed to arise upon doping, the undoped nickelates show no sign of magnetic ordering in experiments. Through a combined density functional …
We study from first principles the magnetic, electronic, orbital and structural properties of the LaMnO3 doped with gallium replacing the Mn-site. The gallium doping reduces the Jahn-Teller effect, and consequently the bandgap. Surprisingly, the system does not go towards a metallic phase because of the Mn-bandwidth reduction. The Ga-doping tends to reduce the orbital order typical of bulk antiferromagnetic LaMnO3 and consequently weakens the antiferromagnetic phase. The Ga-doping favors the G-type orbital order and layered-ordered ferromagnetic perovskite at x=0.50, both effects contribute to…
