Elucidation for search of Dynamical Stripe in YBCO by Inelastic Neutron Scattering Method

本文旨在阐明铜氧化物材料高温超导的基本机理。系统的中子散射研究表明，在单层空穴掺杂LSCO中存在一维“条纹”态动力学结构。为了在各种超导铜氧化物材料中寻找这种独特的“条纹”，我们对典型的高温超导化合物YBCO进行了类似的中子散射测量。由于CuO链中氧的局域有序性可能引起相邻CuO_2面电子结构的变化，因此，氧在该晶体中的控制更成问题。钙替代可能是解决这一难题的一种有前途的方法。因此，我们不能生产任何大的晶体的Ca掺杂的YBCO中子散射实验所需的。相反，我们成功地生长出了大的、单畴的、高质量的、最佳掺杂的YBCO，并首次进行了详细的非弹性中子散射测量。虽然我们没有完成数据分析，但我们至少可以产生新的实验证据，这些证据应该会修改主要出版物中的现有结果。我们还发展了一种新的声子散射实验技术，即超高分辨同步辐射X射线方法。目前，我们可以在超导态下得到LSCO中明确的声子反常的数据，并将其推广到YBCO中类似的测量。由于尚未生长出大单晶，我们认为这种方法是唯一适用于Ca掺杂YBCO散射实验的实验方法。

We aimed to elucidate the basic mechanism of high temperature superconductiity (HTSC) in Cu oxide materials. According to our systematic neutron scattering investigations, one dimensional dynamical structure of 'stripe' state exists in the single layered hole doped LSCO. In order to search this unique 'stripe' in various superconducting Cu oxide materials, we made similar neutron scattering measurements of the typical HTSC compounds of YBCO. Oxygen control in this crystal is more problematic, since the local order of oxygen in CuO chains may, -create the change in the electronic structure in neighboring CuO_2 plane. Ca substitutiqn may be a promising method to solve this difficult problem for our investigation. As a result, we could not produce any large crystal of Ca doped YBCO necessary for neutron scattering experiments. Instead, we were succeeded in growing large, single domain, and high quality, optimum doped YBCO, and have made detailed inelastic neutron scattering measurements for the first time. Though we don't complete the data analysis, we could yield at least new experimental evidence which should revise the existing results in the major publication. We also develop a new experimental technique of phonon scattering by using the ultra high resolution synchrotron X-ray radiation method. At present we could produce the data showing, unambiguous phonon anomalies in LSCO in superconducting state and then extendto the similar measurements in YBCO. We expect that this method is only applicable experimental method for the scattering experiments of Ca doped YBCO, since the large single crystal has never been grown.