Magneto-elastic couplings and superconductivity in 11-type chalcogenides: Thermal and quantum fluctuations

11型硫属化合物超导体的母体Fe_（1 + y）Te化合物具有良好的相图，温度引起的结构和磁性相变依赖于调节参数，如过量Fe的量或流体静压。我们想研究这个系统中不同对称性破缺相变的性质以及磁序参数和结构序参数之间的不寻常耦合。各种调谐参数，如温度，压力，磁场和化学成分，将用于探索相图和定位可能的量子相变。为此目的，高纯度单晶超导和非超导11-硫族化物将合成与精确控制的组成。高压同步加速器X射线衍射将用于确定晶格不稳定性。扫描隧道显微镜（STM）和光谱（STS），中子散射和X射线吸收光谱将被用来调查当地和巡回磁性的不寻常的相互作用。由于STM对电荷敏感，任何自旋轨道耦合或轨道有序都可以在STM图像中以调制电荷密度的形式直接观察到。磁弹性耦合对温度或压力引起的连续的磁性和结构相变在超导附近的影响将使用本地以及批量实验探针与合作在这个优先计划的组合进行调查。这一研究可望区分晶格不稳定性和自旋涨落所起的作用，并揭示该系统中超导的配对机制。

The parent Fe1+yTe compound of the 11-type chalcogenide superconductors has a rieh phase diagram with temperature-induced structural and magnetic phase transitions in dependence of tuning parameters such äs amount of excess Fe or hydrostatic pressure. We would like to investigate the nature of different symmetry breaking phase transitions and unusual couplings between magnetic and structural order parameters in this System. Various tuning parameters, such äs, temperature, pressure, magnetic field, and chemical composition, will be used to explore the phase diagrams and locate possible quantum phase transitions. Forthis purpose, high purity single crystals of both superconducting and non-superconducting 11- chalcogenides will be synthesized with a precise control over the composition. High-pressure Synchrotron x-ray diffraction will be used to determine the lattice instabilities. Scanning tunneling microscopy (STM) and spectroscopy (STS), neutron scattering and x-ray absorption spectroscopy will be used to investigate the unusual interplay of local and itinerant magnetism. Since STM is sensitive to the Charge, any spin-orbit coupling or orbital ordering can be directly observed in the form of a modulated Charge density in an STM Image. The influence of magneto-elastic couplings on temperature or pressure-induced successive magnetic and structural phase transitions in the vicinity of superconductivity will be investigated using a combination of local as well as bulk experimental probes with collaborations within this priority program. This investigation is expected to differentiate roles played by lattice instabilities and spin fluctuatiops and shed light onto the pairing mechanisms for superconductivity in this System.