We report superconductivity in the SmFe0.9Co0.1AsO system being prepared by most easy and versatile single step solid-state reaction route. The parent compound SmFeAsO is non-superconducting but shows the spin density wave (SDW) like antiferromagnetic ordering at around 140K. To destroy the antiferromagnetic ordering and to induce the superconductivity in the parent system, the Fe2+ is substituted partially by Co3+. Superconductivity appears in SmFe0.9Co0.1AsO system at around 14K. The Co doping suppresses the SDW anomaly in the parent compound and induces the superconductivity. Magnetization measurements show clearly the onset of superconductivity with Tcdia at 14K. The isothermal magnetization measurements exhibit the lower critical fields (Hc1) to be around 200Oe at 2 K. The bulk superconductivity of the studied SmFe0.9Co0.1AsO sample is further established by open diamagnetic M(H) loops at 2, and 5K. Normal state (above Tc) linear isothermal magnetization M(H) plots excluded presence of any ordered magnetic impurity in the studied compound.
Competing effects of Mn and Y doping on the low-energy excitations and phase diagram of La$_{1-y}$Y$_{y}$Fe$_{1-x}$Mn$_x$AsO$_{0.89}$F$_{0.11}$ iron-based superconductors
用μ子自旋旋转（$μ$ SR）和$^{19}$ F核磁共振（NMR）研究了Mn对La $_{1-y}$ Y $_{y}$ Fe $_{1-x}$ Mn $_x$ AsO $_{0.89}$ F $_{0.11}$超导体中Fe替代的影响.虽然对于$y = 0$，需要非常低的临界浓度的Mn（$x = 0.2$ %）来淬灭超导电性，但是随着$y$增加，由Y引入的用于La取代的负化学压力稳定了超导电性，并且对于$y= 20$ %，其在Mn含量大一个数量级时被抑制。一旦超导性被抑制，对于$y$ =0和$y= 20$ %，磁相就会出现。低能量的自旋波动引起$^{19}$ F NMR $1/T_1$中的峰值，其起始温度远高于超导转变温度，并且其幅度随着$x$而增加。此外，静态磁相关探测$^{19}$ F NMR线宽测量显示显着增加与Mn含量。根据LaFeAsO $_{0.89}$ F $_{0.11}$接近量子临界点的观点，讨论了超导电性的破坏和磁基态的起始.
In this editorial, we first give a brief survey of the field of iron-selenide superconductivity, both in the case of bulk FeSe characterized by the co-existence of superconductivity and nematic order, and in the case of electron-doped FeSe characterized by high-temperature superconductivity. We next review the 8 contributions to the Frontiers in Physics research topic "High-Tc Superconductivity in Electron-Doped Iron Selenide and Related Compounds".
We determine the phase diagram of LaFe$_{1-x}$Co$_x$AsO single crystals by using nuclear magnetic resonance (NMR). Up to a nominal doping of $x=0.03$, it follows the phase diagram for F-doped polycrystals. Above $x=0.03$, the F-doped samples become superconducting, whereas for Co-doping the structural and magnetic transitions can be observed up to $x=0.042$, and superconductivity occurs only for higher doping levels and with reduced transition temperatures. For dopings up to $x=0.056$, we find evidence for short-range magnetic order. By means of relaxation-rate measurements, we map out the mag…
In this work we revisit the phase diagram of Co-doped LaFeAsO using single crystals and thermodynamic methods. From magnetic susceptibility studies we track the doping evolution of the antiferromagnetic phase, revealing a continuous suppression of $T_\mathrm{N}$ up to 5$\%$ Co doping. In order to study the evolution of the so-called nematic phase, the temperature dependence of the lengths changes along the $a$ and $b$ orthorhombic directions, $ΔL/L_0$, was determined by high-resolution capacitance dilatometry. The results clearly show a gradual reduction of the orthorhombic distortion $δ$ and …
A three-orbital model derived from the two-dimensional projection of the $ab$ $initio$ Hamiltonian for alkaline doped fullerene A$_3$C$_{60}$ with A=Cs,Rb,K is studied by a variational Monte Carlo method. We correctly reproduce the experimental isotropic s-wave superconductivity around the $ab$ $initio$ parameters. With narrowing the bandwidth, the transition to an insulator is also reproduced, where orbital symmetry is found to be spontaneously broken with emergence of an excitonic Mott insulator for two orbitals and an antiferromagnetic insulator nearly degenerate with a spin liquid for the …
Theory for superconductivity in (Tl,K)Fe$_x$Se$_2$ as a doped Mott insulator
本文从掺杂莫特绝缘体的观点研究了最近发现的（Tl，K）Fe $_x$ Se $_2$化合物的可能超导电性。由于Fe空位的存在，Mott绝缘相在$x=1.5$的母体化合物中被检查为优选的。在Fe位的空位的部分填充引入电子载流子并导致电子掺杂的超导电性。在强耦合极限下，利用双轨道哈伯德模型，我们发现在Hund耦合小的情况下，s波配对更有利，而在Hund耦合大的情况下，d $_{x^2-y^2}$波配对更有利.
Non-equilibrium superconductivity in driven alkali-doped fullerides
本文研究了碱金属掺杂富勒烯A $_3$ C $_{60}$中非平衡超导态的形成。在这些材料的超导性的最小三轨道模型中，最近从理论上证明了相互作用的轨道依赖性不平衡导致平衡态下超导性的增强[M. Kim等人Phys.Rev.B94，155152（2016）]。我们调查的动态响应的时间周期性调制的这种相互作用的不平衡，并表明，它导致形成的瞬态超导状态的生存远远超过平衡临界温度$T_c$。对于一个特定的调制频率范围内，我们发现，驱动降低超导性时，施加到超导状态低于$T_c$，而仍然诱导超导状态时，初始温度大于$T_c$。这些发现加强了相关的相互作用不平衡机制作为一个可能的解释最近的实验观察光诱导的超导电性在碱掺杂富勒烯。
Exotic superconductivity in the doped Kitaev quantum spin liquid
Institute for Solid State Physics, University of Tokyo（东京大学固体物理研究所）；Department of Applied Science, Graduate School of Sciences and Technology for Innovation, Yamaguchi University（山口大学理工学综合研究科应用科学系）
I describe the issues of the competing orders in normal state of a parent and Ni-doped iron pnictide superconductor, SrF e 2 As 2 , using LMTO band structure calculation plus multi orbital dynamical mean-field theory. Strong, electronic correlations along with minimal antiferromagnetic instability create a partially gapped Fermi surface, in qualitative agreement with earlier experiments. A good semiquantitative similarity in both normal and ordered state with the earlier experimental transport data is observed along with suppression of magnetic ordering and explained within a correlated, mul- …
An intriguingly complex phase diagram of Na-doped SrFe2As2 is uncovered using high-resolution thermal-expansion, magnetization and heat-capacity measurements. The detailed temperature dependence of the orthorhombic distortion and the anisotropy of the uniform magnetic susceptibility provide evidence for nine distinct electronic phases near the transition region between stripe antiferromagnetism and unconventional superconductivity. In particular, we report the finding of a new magnetic phase which competes surprisingly strongly with superconductivity. From theoretical studies we propose that t…
A spatial interpretation of emerging superconductivity in lightly doped cuprates
最近由Kohleman等人通过扫描隧道显微镜观察到的包括交替的“空穴丰富”和“空穴贫乏”阶梯的域的形成，轻孔掺杂的铜酸盐，被解释在一个有吸引力的机制，有利于存在掺杂的孔位于每个氧原子的一侧上的Cu网站。这种机制导致交替的空穴丰富和空穴贫乏的阶梯的几何图案的周期性等于4倍的晶格间距在CuO平面中，如实验观察到的。引用这篇文章：G. Deutscher，P. G. de Gennes，C. R. Physique 8（2007）.
Hole superconductivity in the electron-doped superconductor PCCO
我们测量了电子掺杂超导体Pr_{2-x} Ce_xCuO_4的电阻率和霍尔角随掺杂和温度的变化。温度为100 K < T <300 K时的电阻率Rho_xx对电子最为敏感。它的温度行为在很宽的掺杂范围内与掺杂无关，甚至对非超导样品也是如此。另一方面，横向电阻率rho_xy或霍尔角θ_H（其中cot（θ_H）= rho_xx/rho_xy）对空穴和电子都敏感。它的温度依赖性受到掺杂的强烈影响，并且cot（theta_H）可以用于识别最佳掺杂（最大Tc），甚至远高于临界温度。这些结果表明，在电子掺杂的铜氧化物中，空穴是超导电性的主要来源。
