相干势近似在关联电子系统中的应用与发展

项目名称： 相干势近似在关联电子系统中的应用与发展

项目编号： No.11474217

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 数理科学和化学

项目作者： 张宇钟

作者单位： 同济大学

项目金额： 80万元

中文摘要： 发展从第一性原理角度出发来理解关联电子材料物理性质的方法是当前凝聚态物理研究领域的热点之一。目前虽然已存在密度泛函理论加U、密度泛函理论加动力学平均场和密度泛函理论加Gutzwiller近似等的方法，但各种方法还存在着各自的局限性。这里我们将发展密度泛函理论加相干势近似的方法。该方法不仅能有效地处理Mott绝缘体状态以及在顺磁相引入自旋涨落，而且能方便地引入空间涨落。同时该方法可用于处理无序的状态，如实验上常遇到的掺杂、取代以及引入杂质后的状态等。为了发展这一可靠的新方法，我们将首先基于模型对一些有趣的强关联物理问题如轨道选择性相变、反常的强关联驱动的绝缘体到金属的相变、双层系统中的量子相变等问题、运用各类相干势近似进行系统的研究，所得到的结果与动力学平均场的结果进行比较，以达到全面理解并进一步改进相干势近似的目的。然后发展第一性原理计算加相干势近似的方法，并应用于理解铁基超导体的相图。

中文关键词： 强关联电子体系；密度泛函理论；铁基超导体；相干势近似；量子相变

英文摘要： Development of methods for understanding the physical properties of correlated materials from first priciples is one of the hot topics in modern condensed matter physics. Nowaday,though a few methods exist such as density functional theory plus U,density functional theory plus dynamical mean field theory, and density functional theory plus Gutzwiller approximation, etc., those methods still have their own limits. Here we will develop another way for understanding the correlated materials from first principles, so called density functional theory plus coherent potential approximation. The coherent potential approximation can not only efficiently deal with Mott insulating state and account for spin fluctuations in paramagnetic state, but also can easily involve the nonlocal spatial fluctuations. Moreover, it can be applied to disordered systems which may appear when doping or substitution is used in experiments. In order to thoroughly understand coherent potential approximation and its recent extensions and develop a new reliable method, we will first apply different kinds of coherent potential approximations to some strongly correlated electronic models where interesting phenomena emerge such as orbital selective Mott transition, anomalous correlation-induced insulator-metal transition and quantum phase transitions in a coupled bilayer system, etc. Part of the obtained results will be compared with those calculated from dynamical mean field theory.Then we will develop density functional theory plus coherent potential approximation based on both plane wave and KKR Green's function methods. Finally, we will apply our developed method to understanding the phase diagram of iron-based superconductors.

英文关键词： strongly correlated electronic system;density functional theory;iron-based superconductors;coherent potential approximation;quantum phase transition