拓扑超导体异质结的输运性质研究

Topological superconductor is one of the research focuses in the field of condensed matter physics. Using non-equilibrium Green's function method and non-commutative topological invariant computation method, we aim to study the transport properties of topological superconductor and its heterojunction in theory. The detail content is included as follows: To study the effects of magnetic impurity and non-magnetic impurity on topological superconductor phase, to uncover the physical reason why the position of one half conductivity plateau measured in the experiment is different to that predicted in theory; To study the effect of one, double, or random domains on the topological properties of quantum anomalous Hall effect and topological superconductor as varing the external magnetic field, to unconver the role of the domain and domain wall in transports of topological superductor heterojunctions; Considering the presence of dephasing because of non zero temperature, to study the competitive mechanism and the critical condition between dephasing and superconductor pairing potential in deriving quantum anomalous Hall state into topological superconductor; To study the transport properties of ferromagnetic-superconductor-ferromagnetic heterojunction, to seek the feasibility of realizing the topological supercondcutor state in this heterojunction. The research result will be of significance to characterize topological superconductor, and will provid key techniques to realized the quantum computation by using Majorana Fermion.

关于拓扑超导体的研究是凝聚态物理领域的研究热点之一。本项目拟利用非平衡格林函数理论及非对易拓扑不变量计算方法，对拓扑超导体体系及其异质结结构的输运性质进行理论研究。研究磁性及非磁杂质对拓扑超导体相边界的影响，揭示实验上拓扑超导体异质结的二分之一电导平台出现位置与理论预测不一致的物理机制；研究单磁畴、双磁畴及随机磁畴存在时，量子反常霍尔态及拓扑超导体在外磁场引起反磁化过程中的拓扑性质变化，探讨拓扑超导体异质结的输运性质变化，揭示磁畴及畴壁运动对拓扑超导体输运性质的影响；引入与温度相关的退相干效应，研究量子反常霍尔态在形成拓扑超导态时退相干与超导配对势的竞争机制及临界条件；研究超导-外尔半金属-超导及铁磁-超导体-铁磁异质结的输运性质，探寻此结构实现拓扑超导态的可行性。研究结果对标征拓扑超导体具有重要意义，将为利用马约拉纳准粒子态实现量子计算提供关键技术。

利用非平衡格林函数、第一性原理计算方法,扫描隧道显微镜及角分辨光电子能谱仪，我们研究了拓扑体系-超导混合结构、节线半金属隧道结、二维锑烯薄膜、第二类型半金属NiTe2等体系的物理特性，研究结果主要包括：1）在修正的Haldane模型-超导结构中发现四端口体系中回路安德烈夫反射系数呈现出关于入射电子能量的非对称性特征，而镜面安德烈夫反射系数却关于入射能量呈对称特征；2）在LC电路观测到了拓扑安德森绝缘体相变；3）在节线半金属结中发现了镜面反射、回路反射、正常透射和镜面透射共存的新奇物理现象；4）从理论和实验的角度，研究二维锑烯、NiTe2、AlSe薄膜等量子材料的外延生长及物性调控机理。