本論文主要藉由同步輻射相關實驗研究三元複合錫化物Sr3Ir4Sn13中二維電荷密度波(two-dimensional charge density wave、2D-CDW)。實驗技術上包括X光散射(X-ray Scattering、XRS)、X光吸收近邊緣結構(X-ray absorption near-edge structures、XANES)、延伸X光吸收精細結構(Extended X-ray absorption fine structure、EXAFS)，探討高品質的 Sr3Ir4Sn13單晶樣品於相變溫度147K (T* ≈ 147 K) 時的電子與原子結構。 X光散射實驗中，在相變溫度下一系列衛星峰的發現，說明可能在沿著(1 1 0)平面上產生了2D-CDW。相變溫度下當沿著(1 1 0)平面，在EXAFS以及相衍生分析中，發現兩種不同的鍵結長度(Sn1(2)-Sn2)，證實了Sn原子的扭曲只發生在(1 1 0)平面上，與2D-CDW有強烈的相關性；而在XANES實驗中，Ir 5d軌域未佔據態的增加以及未佔據態幾乎沒有改變的Sn 5p軌域，說明了在電阻率的變化上，Ir 5d軌域未佔據態的改變相較於Sn 5p軌域扮演較重要的角色。因此在 Sr3Ir4Sn13樣品中，電子以及原子結構與2D-CDW有著密切的關係。 X-ray scattering (XRS), x-ray absorption near-edge structures (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopic techniques were used to study the electronic and atomic structures of high-quality Sr3Ir4Sn13 (SIS) single crystal both below and above transition temperature (T* ≈ 147 K). The evolution of a series of modulated satellite peaks below the transition temperature in XRS experiment indicated the formation of a possible two-dimensional charge density wave (2D-CDW) in the (110) plane. EXAFS phase derivative analysis supports the CDW-like formation by revealing the different bond distances [Sn1(2)-Sn2] below and above the T* in the (110) plane. XANES spectra at the Ir L3-edge and the Sn K-edge demonstrated an increase (decrease) in the unoccupied (occupied) density of Ir 5d-derived states and nearly constant density of Sn 5p-derived states at temperatures T < T*, in the (110) plane. These observations clearly suggest that the Ir 5d-derived states are closely related to the anomalous resistivity transition. Accordingly, a close relationship exists between local electronic and atomic structures and the 2D-CDW-like phase in the SIS single crystal.
