有机拓扑绝缘体的自旋调控与热电性能理论研究

Though the recent studies on thermoelectric properties of topological insulator (TI) materials have become the international hot issues, the reported TI materials with very low thermalelectric figure of merit (ZT value) immensely restrict the development in thermoelectric application. In this project, we proposed a type of new organic TI materials with related thermoelectric properties research. Primarily, we explore this type of materials on quantum anomalous Hall effects based on constructed transition-metal-organic-framework (MOFs), and filter out the appropriate organic TI with minor band gaps. Secondly, determine the optimal junction point between electrical and thermal conductivities of high performance thermoelectric materials. As increasing the electrical conductivity of the materials, the lattice thermal conductivity will decrease, which leads to improve the thermoelectric performance of materials. Finally, build the related models of nano-wires, nano-ribbons, and nano-films based on filtered organic TI materials with quantum anomalous Hall effects, which aims to design the organic TI materials with outstanding spin-filtering effects. The successful facilitation of the project will broaden the selection range for thermoelectric materials, and accelerate the pace of applications into thermoelectrics. Meanwhile, the findings of singlet spin state in the selected organic TI with quantum anomalous Hall effects will set-up the theoretical foundation for spintronics device research and development.

近几年，拓扑绝缘体的热电性质研究成为了国际研究热点。然而，难以提高的热电优值（ZT）限制了这一类材料在热电领域应用发展。在此项目中，我们提出一类新型拓扑绝缘体材料-有机拓扑绝缘体，并研究这一类材料的热电性能。首先，通过搭建金属有机框架（MOFs），探寻呈现量子反常霍尔效应的有机拓扑绝缘体。并筛选出微隙拓扑绝缘体材料。然后，确定高热电性能材料电导和热导的最佳结合点，在提高材料电导率的同时，降低材料晶格热导率，进而提高材料的热电性能。最后，选择在费米能附近存在单一自旋态的有机拓扑绝缘体，并进一步构建纳米线、纳米带与纳米膜结构模型，设计出具有优异自旋过滤效应的有机拓扑材料。本项目成功实施将扩展热电材料选择范围，并加快其在热电领域应用步伐。同时，呈现量子反常霍尔效应的有机拓扑绝缘体中发现的单一自旋态为自旋器件发展提供理论支持。

本课题主要针对有机材料的热、电性质与自旋输运性质研究。由于二维有机拓扑材料的结构不稳定性，导致对基于晶格动力学与分子动力学的热输运性质研究困难。我们及时调整研究方向。利用ATK、VASP等软件，研究了有机分子链的电子自旋输运性质。基于晶格动力学及分子动力学方法，研究了有机分子链、纳米带、纳米线等材料的热性质。基于紧束缚模型、格林函数方法、重整化群方法、研究了硅稀等二维拓扑材料的电子自旋输运性质、磁响应特性。利用粒子群优化结构搜索算法结合第一性原理计算研究了叠氮化铷RbN3在高压下的结构演化。研究高压下芳香分子与C20混合物的高压性质。利用我们发展的共价键晶体搜索程序，发现了两类硼氮多晶结构，L-BN和X-BN，研究发现一类新的碳同素异构体C48(2i+1)。这些碳的通俗异构体由4、8碳环构成。研究过程基本能够按照原定的计划进行，特别是有机纳米链的自旋输运性质，为分子自旋过滤器的实现提出了可行性方案。相关研究结果发表在Physics Review B、RSC Advance、Scientific Reports、J. Phys.: Condens. Matter等SCI刊物，共25篇，其中第一作者论文11篇、通讯作者论文6篇。共申请国家发明专利7项，获批3项。后续有4篇SCI论文将在2018年刊出。