High-quality superconducting KxFeySe2 single crystals were synthesized using an easy one-step method. Detailed annealing studies were performed to make clear the phase formation process in KxFeySe2. Compatible observations were found in temperature-dependent X-ray diffraction patterns, back-scattered electron images and corresponding electromagnetic properties, which proved that good superconductivity performance was close related to the microstructure of superconducting component. Analysis based on the scaling behavior of flux pinning force indicated that the dominant pinning mechanism was delta(Tc) pinning and independent of connectivity. The annealing dynamics studies were also performed, which manifested that the humps in temperature-dependent resistance (RT) curves were induced by competition between the metallic/superconducting and the semiconducting/insulating phases.
High resolution characterisation of microstructural evolution in Rb$_{x}$Fe$_{2-y}$Se$_{2}$ crystals on annealing
已知相分离的A $_x$ Fe $_{2-y}$ Se $_2$化合物的超导和磁性取决于生长后的热处理和冷却曲线。本文着重研究了退火过程中微观结构的演变，以及退火对Rb $_x$ Fe $_2-y$ Se $_2$晶体超导性能的影响。我们发现，生长的晶体中的少数相具有增加的晶胞各向异性（c/a比），减少Rb含量和增加Fe含量相比，矩阵。微观结构相当复杂，具有沿{113}惯面排列的两相介观板状特征。少数相在{113}平面上强烈地刻面，我们已经表明通过使作为相变的结果引入的体积应变能最小化来驱动。在488 K退火导致粗化的介观板状特征和第三个不同的相的形成。晶体中少数相的结构和化学性质的微妙差异被认为是超导转变温度变化的原因。此外，扫描光电子显微镜已经清楚地表明，少数相的电子结构具有较高的低结合能Fe 3d轨道的占据态密度，这是表现出超导性的晶体的特征。这表明具有高c/a比的Fe-无空位相与超导相的电子结构特征之间存在明显的相关性。
Annealing-enhanced spin-orbit effects in non-centrosymmetric superconducting NbRe films
Technische Universität Braunschweig（布伦瑞克工业大学）；Istituto di Struttura della Materia of the National Research Council（国家研究委员会物质结构研究所）；Università degli Studi di Salerno（萨莱诺大学）；CNR-SPIN（意大利国家研究委员会自旋物理研究所）
