Floquet Weyl半金属的准粒子相干及杂质调制的磁电输运理论研究

Weyl semimetals (WSMs) are a new type of topological materials, whose ultrahigh mobility and spectacular transport properties can be of potential applications in the future high-speed electronic devices. How to identify the chiral anomaly of the WSMs has become one of the most hotpot in the field of condensed matter physics. In this project, we aim to investigate the magnetotransport and quasiparticle interference in WSMs under perturbations of the impurity scattering and time periodically driving, during which we would emphasize the effect of the impurity-induced resonant states on the chiral anomaly. The contents are included as follows. 1) Studying the effect of different types of (charged or magnetic) impurities on the magnetotransport in WSMs and providing new theoretical foundations for identifying WSMs; 2) Studying the effect of the impurity scattering on the surface Fermi arcs of the Floquet WSMs and illuminating the quasiparticle interference characters of the Floquet WSMs; 3) Studying the electron transport of the magnetically-doped WSMs and exploring the methods for controlling the properties of the WSMs. This project, on one hand, could investigate the physical properties of Floquet WSMs, and on the other hand, it also could provide theoretical foundation for exploitation of the WSM-based high-speed electronic devices.

外尔(Weyl)半金属是一种新型的拓扑材料，其超高的载流子迁移率和不同寻常的电子输运性质在未来的高速电子器件中具有潜在的应用价值。如何判定Weyl半金属的手征反常是凝聚态物理领域的研究前沿和热点。本项目拟研究Weyl半金属在杂质和周期驱动共同作用下的磁电输运及准粒子相干效应，突出杂质共振态对手征反常的影响。具体研究内容包括：1)研究不同（静电或磁性）杂质对Weyl半金属磁电输运的影响，为鉴定Weyl半金属提供新的理论依据；2)研究杂质散射效应对Floquet Weyl半金属表面费米弧的调制作用，阐明Floquet Weyl半金属的杂质散射规律；3)研究磁掺杂Floquet Weyl半金属的输运性质，探讨调控Weyl半金属性质的多重手段。本项目不仅可以探究Floquet Weyl半金属的物理性质，还可为开发基于Weyl半金属的高速电子器件提供理论基础。

拓扑半金属具有拓扑量子反常，相关的拓扑输运现象由一定的拓扑不变量保护，不受杂质散射影响，并对材料的细节不敏感。本项目研究了拓扑半金属在强磁场和弱磁场下的线性磁电输运，发展了拓扑半金属的线性磁电输运理论，并提出利用磁电效应探测拓扑量子反常的多种机制，包括：研究了无序Weyl半金属中的近藤效应，发现由于手征反常，近藤峰可以受平行的电场和磁场调控，并提出利用电可调的近藤效应直接测量Weyl半金属的手征反常；研究了有限尺寸Weyl半金属中的磁电阻输运，由于手征反常，Weyl半金属正纵向磁导对电场和磁场的角度依赖会变窄，解释了相关的实验现象；研究了倾斜Weyl半金属中的磁电阻效应，通过将动量的高阶项引入到传统的低能有效哈密顿量中，发现塞曼场将会导致Weyl锥倾斜，进而产生跟手征反常类似的负磁阻效应以及pi周期的平面霍尔效应，由此，我们提出负磁阻和平面霍尔效应只是观测手征反常的必要条件，而不是充分条件。此外，我们还探究了拓扑材料的光致拓扑相变及相关的量子输运，首次提出Weyl-half metal 相的概念，并阐述了手征反常和拓扑泵浦之间的密切关系，提出利用交流电代替磁场探测手征反常和手征磁效应。本项目的研究，有助于人们深入理解拓扑半金属的内在物理，为设计相关的电子器件提供理论依据。