二维材料异质结构热电输运的界面效应与应变效应

Two-dimensional material heterostructure is an important kind of new nanomaterial, which has important application in the fields of thermoelectric energy and microelectronics，and other high-tech industries in our country. Due to the profound interface and strain effects, Two-dimensional material nanodevices exhibit very novel thermoelectric transport properties. However, up to now such study is still in its infancy and the physical mechanism for such phenomenon is still unclear. Because of the complex structure and strong electron-phonon interaction of two-dimensional material heterostructures, the current computational methods and codes are no longer applicable. As a result，very little theoretical research in this field has been done so far. In this project, based on the non-equilibrium Green's function theory and Feynman diagram technology, we will derive the self-energy and response coefficients formula, which effectively describe electron-phonon interaction in thermoelectric transport. Starting from typical two-dimensional material heterostructures, we will systemically study the interface and strain effects on the thermoelectric transport properties, and explore the underlying mechanism in the concept of the microscopic electron and phonon transport theory. On this basis, in use of size, substrate, defects, external fields and other means, we will modulate the transport properties of two-dimensional material heterostructures via designing the composition and structure, manipulate the interface and strain of two-dimensional material heterostructures to provide the theoretical basis for the development of novel-high-performance thermoelectric and microelectronic devices.

二维材料异质结构是一类重要的新型纳米材料，在热电能源和微电子等高科技产业应用前景广阔。由于界面与应变效应显著，二维材料微纳器件展现出非常新奇的热电输运特性。目前相关研究还处于起步阶段，人们对其物理机制的认识尚不清晰。由于二维材料微纳器件具有复杂的结构，强烈的电子-声子相互作用，现有的计算方法程序不再使用，导致了相关理论研究甚少。本项目拟从非平衡格林函数理论和费曼图形技术出发，获得有效描述热电输运中电声相互作用的自能及响应系数表达式；从典型的二维材料异质结构入手，系统计算研究界面、应变与二维材料异质结构热电输运性质的耦合关联，结合电、声子输运理论探索其微观机制；通过设计二维材料结构与成分，利用尺寸、基底、缺陷、外场等手段，调控其界面与应变获得具有理想热电输运性质的二维材料异质结构，为设计高性能纳米热电器件提供理论依据和技术指导。

由于界面与应变效应显著，二维材料微纳器件展现出非常新奇的热电输运特性。目前相关研究还处于起步阶段，人们对其物理机制的认识尚不清晰。本项目从典型的二维材料异质结构入手，系统计算研究界面、应变与二维材料异质结构热电输运性质的耦合关联，结合电、声子输运理论探索其微观机制；通过设计二维材料结构与成分，利用尺寸、基底、缺陷、外场等手段，调控其界面与应变获得具有理想热电输运性质的二维材料异质结构。结果如下：(1) 提出电导各向异性的方向和大小强烈地依赖于化学势，获得与实验观测一致的结果。同时，通过施加外加电场可以调控电导各向异性的的方向和大小。(2) 提出边缘缺陷可以大幅提高锯齿形和扶手型锗烯纳米带的热电输运性质。同时，外加电场对锗烯纳米带热电输运性质的调控显著。(3) 通过界面耦合，首次在硅烯上实现量子反常霍尔效应，并构造其最小有效紧束缚模型。(4) 通过应变效应，设计Hf和graphyne的复合结构，实现大带隙的磁性拓扑绝缘体。这些结果为基于二维材料异质结构的纳米电子器件设计提供了有益的理论指导。