本文对Fe $_{1.05}$ Te单晶的输运、比热、磁化率和光谱进行了综合研究。我们证实Fe $_{1.05}$ Te在65 K附近发生一级相变。然而，它的物理性质是相当大的不同，从其他母体化合物的FeAs为基础的系统，大概是由于过量的Fe离子的存在。在转变温度以上的电荷输运是不相干的，并且在转变温度以下没有观察到明显的带隙特征。在掺Se的超导样品Fe $_{1.03}$ Se $_{0.30}$ Te $_{0.70}$中也存在强的杂质散射效应，导致T $_c$较低，但上临界场较高。
英文摘要：
We report on a comprehensive study of the transport, specific heat, magnetic susceptibility and optical spectroscopy on single crystal of Fe$_{1.05}$Te. We confirm that Fe$_{1.05}$Te undergoes a first-order phase transition near 65 K. However, its physical properties are considerably different from other parent compounds of FeAs-based systems, presumably attributed to the presence of excess Fe ions. The charge transport is rather incoherent above the transition, and no clear signature of the gap is observed below the transition temperature. Strong impurity scattering effect exists also in Se-doped superconducting sample Fe$_{1.03}$Se$_{0.30}$Te$_{0.70}$, leading to a relatively low T$_c$ but a rather high upper critical field.
Surface electronic state of superconducting topological crystalline insulator
研究了掺杂拓扑晶体绝缘体在超导态下的表面态。受Sn $_{1-x}$ In $_x$ Te的启发，我们考虑了完全带隙的对势，计算了表面光谱函数。发现在（001）面出现了镜保护的零能Andreev束缚态，这些束缚态可以沿表面布里渊区的镜对称线运动。我们还表明，表面Andreev束缚态的变化系统的掺杂由于在正常状态下的狄拉克表面状态的存在。
Electronic Structure of Single Crystalline NdO$_{0.5}$F$_{0.5}$BiS$_{2}$ Studied by Angle-resolved Photoemission Spectroscopy
NdO $_{0.5}$ F $_{0.5}$ BiS $_{2}$是一种新的层状超导体。用角分辨光电子能谱研究了超导转变温度为4.87K的单晶NdO $_{0.5}$ F $_{0.5}$ BiS $_{2}$超导体的低电子结构。费米面由X点周围的两个小电子袋组成，沿$k_z$方向几乎没有翘曲。我们的结果表明，多带和二维的电子结构的性质。光电发射数据和能带计算之间的良好的协议给出的重整化因子为1，表明在这种材料中的电子关联相当弱。此外，我们发现实际的电子掺杂水平和费米表面尺寸比名义成分预期的要小得多，这在很大程度上可以用铋的缺乏来解释。小的费米口袋尺寸和弱的电子关联在这里发现强有力的理论约束，并建议BiS $_2$基超导体可能是传统的BCS超导体介导的电子-声子耦合。
The details of the superconducting to quantum metal transition (SQMT) at T=0 are an open problem that invokes much interest in the nature of this exotic and unexpected ground state1-3. However, the SQMT was not yet investigated in a crystalline 2D superconductor with coexisting and fluctuating quantum orders. Here, we report the observation of a SQMT in 2D ion-gel gated 1T-TiSe24, driven by magnetic field. A field-induced crossover between Bose quantum metal and vortex quantum creeping with increasing field is observed. We discuss the interplay between superconducting and CDW fluctuations (dis…
Electronic structure of single-crystalline Mg$_x$Al$_{1-x}$B$_2$ probed by x-ray diffraction multipole refinements and polarization-dependent x-ray absorption spectroscopy
单晶Mg $_x$ Al $_{1-x}$ B $_2$的X射线衍射多极子精细结构和B1 $s$边的偏振相关的近边X射线吸收精细结构揭示了强各向异性的电子结构。比较超导化合物（$x= 0.8$，1.0）与非超导化合物（$x=0$）的数据，给出了硼$p_z$键杂化重排的直接证据，并强调了$σ$键合共价态$sp^2$中空穴对二硼化物超导性质的重要性。数据表明，镁是大约二价的MgB $_2$和建议主要是离子键之间的镁离子和二维B环。另一方面，对于AlB $_2$（$x=0$），每个Al原子约1.5个电子转移到B片，而剩余的1.5个电子保留在Al位点，这表明Al离子和B片之间存在显著的共价键合。这一发现与静态电子形变密度一起表明MgBPDMATHABMO和AlBPDMATHABMO的B片上的电子数几乎相等，但在$σ$和$π$键之间具有完全不同的电子/空穴分布。
Electronic structure of single-crystalline Sr(Fe$_{1-x}$Co$_x$)$_2$As$_2$ probed by x-ray absorption spectroscopy: Evidence for isovalent substitution of Fe$^{2+}$ by Co$^{2+}$
利用Fe、Co和As的$L_{2,3}$边的近边X射线吸收精细结构研究了Sr（Fe $_{1-x}$ Co $_x$）$_2$ As $_2$（$x =$ 0、0.05、0.11、0.17和0.38）化合物的价态和自旋态构型与取代位的关系.目前的数据提供了直接的光谱证据的有效等价取代Fe $^{2+}$由Co $^{2+}$，这是在广泛假设的Co诱导的电子掺杂效应。此外，数据显示，不仅Fe价态在整个掺杂范围内保持完全不受影响，Co和As价态也是如此。这些数据强调了一个突出的作用之间的杂化（Fe，Co）3 $d_{xy}$，$d_{xz}$，$d_{yz}$轨道和作为$4s/4p$状态的能带结构在$A$（Fe $_{1-x}$ Co $_x$）$_2$作为$_2$和建议的（Fe，Co）-As键的共价性是磁性和超导性之间的相互作用的一个关键参数。
Doped BaCoSO was recently predicted to be a high-temperature superconductor in a new class based on Co and Ni. Using a Co-S self flux method, we synthesized single crystals of the antiferromagnetic insulator BaCoSO. Our magnetic and specific heat measurements and neutron diffraction provide details of its magnetic anisotropy and order. Its band gap was determined to be about 1.3 eV by our measurements of its photoemission spectrum and infrared optical conductivity. Our results can pave the way to exploring the predicted superconductivity in this Co-based material.
Utilization of mechanical alloying method for flux growth of single crystalline BaFe$_2$(As$_{1-x}$P$_x$)$_2$
采用机械合金化法制备了Ba-Fe-As-P前驱体，为Ba-（As，P）助熔剂法生长BaFe $_2$（As $_{1-x}$ P $_x$）$_2$单晶提供了必要的前驱体。通过机械合金化，Ba-（As，P）前驱体在室温下在1小时内成功形成，显著缩短了制备时间。采用机械合金化前驱体，生长出尺寸达5~ mm $\times$ 5~mm $\times$ 0.1~ mm的BaFe $_2$（As $_{1-x}$ P $_x$）$_2$单晶。
Electronic and magnetic properties of the heavily H-doped LaFeAsO$_{1-x}$H$_x$ $(x\sim0.5 )$ were studied in the framework of the density functional theory combined with the dynamical mean field theory (DFT+DMFT). We found a stripe-like-ordered structure of hydrogen and oxygen atoms, as a ground state, with the same configuration as the antiferromagnetic (AF) order. The new configuration could explain the existing experimental results related to the heavily H-doped LaFeAsO$_{1-x}$H$_x$, such as an in-plane electronic anisotropy and a non-uniform magnetic behavior. A significant anisotropy was …
