拓扑绝缘体中新奇的量子散射效应

Recently, due to the significant advances of the topological iunsulator (TI) and the great improvement of the scanning tunneling microscopy, the novel quantum scattering effect in TI has become an important issue in the morden condensed matter physics. In this program, we would like to explore thoroughly this frontier issue, and carry out some innovative and fundamental researches for applications. The research contents mainly focus on the following four problems. Firstly, we will study the anomalous Aharonov-Bohm oscillations and the analogous weak (anti-)localization effects in the local density of topological surface states induced by double impurities, and compare with the case of the ordinary two-dimensional electron gas; Secondly,the novel scattering phenomena, such as Kondo resonance, quantum images, spin-polarization and inelastic spin scattering effect, arising from the Kondo impurities localized in the quantum corrals on TI surface will be investigated theoretically; Thirdly, we will also discuss thoroughly the resonant tunnelling through step barriers of Dirac fermions on TI surface, the anisotropic Fabry-Pérot resonance effects confined in nano-steps, the life time of quasiparticles,and the physical properties of the electric current as well as the spin surrent of Dirac electrons on TI surface within steps; Last but not least, the anisotropic Klein tunnelling of Dirac fermions on TI surface and the spin-polarization effect in Klein tunnelling need to be studied theoretically. Our researches in this program may enhance the understandings on the quantum scattering effects, and promote the development of studies about the TI materials and the interrelated spin-orbit coupling systems.

近年来由于在拓扑绝缘体方面取得的重大进展和扫描隧道显微镜技术的蓬勃发展，使得研究拓扑绝缘体材料中新奇的量子散射效应成为当前凝聚态物理中一个重要的前沿问题。本项目拟对这一前沿问题开展深入探索，做出具有创新意义的应用基础研究工作。研究内容主要包括：拓扑绝缘体中双杂质引起的局域电子态密度反常Aharonov-Bohm 振荡效应，类弱反局域与类弱局域效应，并比较一般二维电子气的异同；阐述拓扑绝缘体表面量子栅栏系统中的近藤杂质带来的新奇散射现象，如近藤共振、量子镜像、自旋极化、自旋非弹性散射等；深入研究拓扑绝缘体表面台阶散射引起的狄拉克电子的共振隧穿、各向异性的法布里-帕罗共振效应、准粒子寿命、电流及自旋流分布等物性；理论探索拓扑绝缘体中狄拉克费米子各向异性的克莱因隧穿，及其自旋极化效应。本项目的研究工作会推进人们对量子散射效应的认识，促进拓扑绝缘体材料及相关的自旋-轨道耦合系统研究的发展。

本项目研究拓扑绝缘体中新奇的量子散射效应。项目执行期间，我们研究了拓扑绝缘体表面平行双台阶之间的各向异性法布里-帕罗共振态，揭示了能带弯曲的重要作用；与STM/STS实验结合研究了Bi2Te3表面等边三角形量子栅栏对狄拉克电子的量子囚禁，发现了拓扑表面共振态并阐明了其中的物理机制；研究了单层石墨烯中狄拉克电子局域态密度的反常AB 振荡效应，揭示了狄拉克电子体系与传统二维电子气之间的异同；讨论了石墨烯表面杂质原子对的间接长程Friedel振荡相互作用，并得到了其振荡衰减的解析表达式；研究了二硫化钼单层膜中杂质缺陷引起的带间共振态，发现自旋轨道耦合会导致共振峰发生劈裂；研究了电荷掺杂和应变对过渡金属硫化物 1T-TiSe2 中的电荷密度波态转变的影响，得到了转变温度随掺杂浓度以及应变强度的变化规律；还初步讨论了电荷掺杂和应变对1T-TiSe2 结构稳定性的影响，得到了应变结构稳定的临界掺杂浓度；讨论了拓扑绝缘体薄膜异质结结构中的电子—空穴对、拓扑超导体近邻效应、以及铁基超导体的准粒子占据数布居等；此外，还将凝聚态理论中的量子散射理论拓展和应用到等离子体中的能量弛豫问题的理论研究中，获得了一系列有意义的结果。这些研究工作将可能促进我国在量子散射理论方面的研究进展.