类高温超导准二维体系的人工构建与电子结构研究

高温超导机理的研究一直是凝聚态物理中的热点和挑战。然而高温超导至今只有铜基和铁基两类体系，既难以从复杂的物理表象中甄别高温超导的关键因素，也难以在现有体系内部验证理论猜想。根据高温超导材料的特性，构建类似体系，从中探索高温超导，验证理论图像，是突破研究瓶颈的重要途径，而最近镍基新超导的发现为此提供了重要方向。本项目拟利用分子束外延技术构建类高温超导准二维体系，具体包括模拟铜基超导的两类镍氧化物和模拟铁基超导的钴基化合物薄膜，利用低温退火、化学掺杂、衬底应力、以及超晶格设计等调控其晶格、掺杂和轨道构型，在合适的参数空间寻找超导相。结合角分辨光电子能谱、共振X射线散射等同步辐射表征技术，对材料体系的电子结构、轨道构型、玻色子元激发进行系统观测，揭示多种自由度相互耦合的普遍规律。根据超导出现的规律，甄别超导的关键要素及现有理论图像。预期这些结果将为高温超导理论的最终建立提供实验判据。

Research on the mechanism of high temperature superconductivity has always been the central challenge in condensed matter physics. However, there are only two types of high-Tc superconductivity systems, copper-based and iron-based systems. It is difficult to distinguish the key factors of high-temperature superconductivity from their complicated physical appearance, and it is difficult to verify the theoretical proposes within the existing systems. Constructing materials that resembles the high-temperature superconductors, exploring high-temperature superconductivity in them, and testing the theoretical pictures, are important ways for breakthrough research, and the recent discovery of new nickel-based superconductor points an important direction. In this project we will use molecular beam epitaxy to construct quasi-two-dimensional systems that mimic high-temperature superconductors, including two types of nickel oxide for copper-based superconductivity and a cobalt-based compound film for iron-based superconductivity. Through low-temperature annealing, chemical doping, substrate strains, and superlattice design, we will tune its lattice, doping, and orbital configuration, and look for superconductivity in the appropriate parameter space. Combining angle-resolved photoelectron spectroscopy, resonant X-ray scattering and other synchrotron radiation techniques, we will systematically study the electronic structure, orbital configuration, and boson element excitation of these systems, to reveal the general rule of coupling between multiple degrees of freedom. According to the pattern of the emergence of superconductivity, we can identify the key elements of superconductivity and test the existing theoretical pictures. We expect that these results will provide experimental criteria for the final establishment of the theory of high temperature superconductivity.