铀的电荷密度波转变及维度调控研究

项目名称： 铀的电荷密度波转变及维度调控研究

项目编号： No.11504342

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 陈秋云

作者单位： 中国工程物理研究院

项目金额： 24万元

中文摘要： 金属铀除了在常温常压下具有较低的晶格对称性，在低温区域还具有奇异的电荷密度波和超导特性。铀也是目前已知的唯一在低温下同时存在电荷密度波和超导两种量子有序态的金属单质材料，且是一种三维电荷密度波材料。这些特殊性质与其电子结构密切相关，但是关于铀低温下电子结构的研究工作还很缺乏。维度调控能够引起电子结构的明显变化，预期能够对电荷密度波起到明显的调制作用。本申请项目拟采用分子束外延生长技术在不同的基底上生长铀单晶薄膜，通过生长不同层数的铀薄膜来调控其维度，利用低能电子衍射、角分辨光电子能谱仪、低温扫描隧道显微镜/低温扫描隧道谱等超高真空技术手段，对其表面形貌、晶体结构和电子结构进行研究，获得电荷密度波转变前后晶体结构和电子结构的变化情况，以及维度对电荷密度波和电子结构的影响，并结合第一性原理计算，理解铀的低温相变机制。

中文关键词： 铀；电荷密度波；角分辨光电子能谱；扫描隧道显微镜；维度调控

英文摘要： Except for its low-symmetric crystal structure at ambient pressure and temperature, uranium (U) is unique for the charge density wave (CDW) and superconductivity in the low temperature region. U is also the only metallic elementary material which exhibits both CDW and superconductivity at low temperatures. Moreover, U is a three-dimensional CDW material. All these exotic properties are closely related with its electronic structure at low temperatures, which is still deficient to date. Dimension control plays an important role in the change of electronic structure, and it is predicted that it may have great influence on the CDW. In this proposal, we propose to grow U films on different substrates, and thickness dependent thin films will also be grown to obtain the dimension control of U. By using low energy electron diffraction, angle-resolved photoemission spectroscopy, scanning tunneling microscopy and scanning tunneling spectroscopy, we are going to probe the crystal structure and electronic structure of the U films before and after CDW transition. With the aid of first principles calculations, we aim to understand the mechanism of the CDW at low temperature and how dimension influences it.

英文关键词： uranium;charge density wave;angle-resolved photoemission spectroscopy;scanning tunneling microscopy;dimension control