重原子铱氧化物关联体系的物性研究

For heavy 5d atoms, their band spatially extended more than that of 3d atoms in the same group. The larger spatial extent of wave functions means that the on-site Coulomb repulsion is smaller. Therefore the 5d materials are generally less strongly correlated than 3d materials. In the mean time, as the atomic mass increases, the spin-orbital coupling (SOC) is stronger than that of the 3d atoms. The energies of the two couplings is of same order of magnitude, but change a little in different structure and element compounds. Usually, each of them is smaller than the 5d band width. They compete and/or corporate to dominate the physical properties of 5d compounds, leading to a lot of exotic phenomena. Our main focus of this project is to investigate the newly founded exotic physical properties of heavy atom iridium oxides. Based on various sample preparing instruments and experience, abundant experimental instruments in our group, we plan to prepare high quality iridium oxides and new compounds. For structural and physical properties characterizations, high sensitive X-ray diffractometer, EDX, Quantum Design MPMS-XL Squid, PPMS, and so on will serve as an excellent platform. We will study the rich physical properties of the iridium oxides, such as e-e correlation effect, phase transition,variores ordering competition, by tuning the effect elements,charicterize.the physical properties for new materials by using MPMS and PPMS, including.resistivity, magnetic properties, specific heat, thermo-power, Hall coefficient,.and so on. Furthermore, we could reveal their band structure and electronic dynamics near the Fermi level by optical reflectivity measurement and analysis, which dominates lots of physical properties of the compounds. It is also an effect way to verify the first-principle calculations and deepen the other experimental researches.

本项目计划探索研究重原子铱系列氧化物的新涌现的奇异物理性质。相对于同族3d原子，5d.铱原子质量重，原子半径大，相应地自旋轨道耦合作用变更强，同格点上电子关联作用变弱。二者处于同等量级，但在不同结构和元素的物体中稍有差别，在多数情况下各自也都比能带宽度小，在这样的体系里往往是这些因素竞争与合作，共同发挥作用决定了材料的物理性质，而各自由度在合作中的权重极大地影响了最终的结果，导致很多奇异的物理现象。能有效调节各影响因素是探究现象背后的机制，发现新现象的关键。我们期待在本小组优良的样品制备条件和多样的红外谱及常规结构和物性测量设备及我们多年的相关的研究积累的基础上，通过对有奇异物性的铱氧化物如关联体系，出现的金属绝缘体相变、竞争序等深层次丰富物性，开展更深层次如电子结构和电子态行为、自旋结构和自旋激发等多个方面全面细致物性研究。

本课题中我们主要进行了铱氧化物的多晶和单晶样品制备以及物性研究。我们与同事们合作对稀有的国际上迄今3D材料中第二个可能的Slater金属-绝缘体相变(MI)材料SrIr0.8Sn0.2O3进行了变温的红外反射率谱测量及分析研究，观测到能隙仅在反铁磁有序温度以下连续打开的过程及光电导实部在能隙低能边缘特殊的频率依赖关系，从电荷动力学角度和能带结构的角度提供了发生在其中的MI转变是Slater型的确凿实验依据，进一步证实第二个Slater MI相变材料并丰富了此类型相变的认识。结合国际前沿的发展，作为课题的延伸我们还与同事合作探索有近似结构的t2g能带在费米面附近的过渡族材料中不同程度形式的自旋交换作用对电子输运性质的影响。反复对高压下超导体MnP进行非极化/极化红外反射率谱测量和分析，发现螺旋磁有序后一极化方向部分载流子被gap掉且两种载流子模型可以对MnP红外谱低频特征进行合理解释，结合杨义峰研究员的理论计算深入研究表明MnP中存在轨道选择的电荷动力学性质，首次揭示MnP的螺旋磁有序并非以往的纯局域磁矩机制。此外我们和原中山大学吴东老师合作，发现4d/5d新材料EuSbTe3具有宽光学响应的优良性质。本项目在SCI收录的杂志上发表论文项目标注的3篇，未标注的2篇。另有待发表1篇。