The electronic structure and related physical properties of correlated electron systems

强关联的电子系统展示了一些最有趣的物理性质，对目前和未来在电子设备、可持续能源、生物医学设备、交通甚至量子计算方面的应用都很重要。由过渡金属和稀土化合物(如它们的氧化物)制成的材料通常表现出极端的性能，如高温超导、高热电性能、高介电常数、巨大的磁阻等。这些材料不同于像硅这样的传统半导体或像铝这样的简单金属，在这些材料中，电子在原子之间移动的电荷在决定应用中起着重要的作用。过渡金属氧化物通常是电绝缘体和磁性的，因为电子之间有很强的排斥作用。然而，化学替代可以将这种磁性绝缘体转变为高温超导体(1988年诺贝尔奖)，并导致它们的性质发生其他戏剧性的变化。支配它们行为的基本物理学仍然是现代科学研究中最大的智力挑战之一。在这里，自旋和轨道自由度以及它们与电子的电荷自由度的相互作用起着至关重要的作用。近年来，随着利用原子逐个沉积的方法物理制备新型氧化物材料的发展，基于界面的全新材料和性质被展示出来，为材料科学和器件应用开辟了新的方向。我们将利用我们在不列颠哥伦比亚大学开发的新的实验设备和加拿大光源进行共振X射线散射和原位原子对原子材料的制备，并将这些与新的理论见解一起应用于战略选择的过渡金属氧化物的表面、工程界面和纳米结构的研究。这种新的设备特别适合于研究埋藏界面的电子结构，这些界面很难或不可能用其他方法以非破坏性的方式访问。在这些界面上发现的壮观特性被预测为可能形成下一代电子设备的全新平台。

Strongly correlated electron systems exhibit some of the most interesting physical properties important for present and future applications in electronic devices, sustainable energy, biomedical devices, transportation and perhaps even quantum computing. Materials made of transition metal and rare earth compounds such as their oxides are examples often exhibiting extreme properties such as high temperature superconductivity, high thermoelectric power, high dielectric constants, colossal magneto resistance and many more. These materials are different from conventional semiconductors like Si or simple metals like Al in which the charge of the electrons moving in amongst atoms plays the important role in determining the applications. Transition metal oxides often are electrical insulators and magnetic because of the strong repulsive interaction between the electrons. However chemical substitution can turn such magnetic insulators into high temperature superconductors (Nobel Prize 1988) and cause other dramatic changes in their properties. The basic physics governing their behaviour remains one of the biggest intellectual challenges of modern scientific research. Here the spin and orbital degrees of freedom and their interplay with the charge degrees of freedom of electrons play essential roles. With the recent development of the physical preparation of new oxide materials using an atom by atom deposition approach completely new materials and properties based on interfaces have been demonstrated opening up a new direction in material science and device applications. We will utilize the new experimental facilities we developed at UBC and the Canadian Light source for resonant X ray scattering and in situ atom by atom material preparation and apply these together with new theoretical insights to the study of surfaces, engineered interfaces and nanostructures of strategically selected transition metal oxides. This new facility is especially suited to study the electronic structure of buried interfaces which are hard or impossible to access in a non destructive manner with other methods. The spectacular properties found at such interfaces are predicted to potentially form a whole new platform for the next generation of electronic devices.