拓扑绝缘体量子点中的磁交换相互作用

从理论上研究了拓扑绝缘体量子点中的磁交换相互作用.在拓扑绝缘体量子点中,边缘态电子数可以通过量子点的尺寸和外加电场进行调控.当量子点中掺入单个磁离子并且边缘态填充奇数电子时,电子与单个磁离子之间的交换相互作用达到最大值;而边缘态填充偶数电子时,电子与单个磁离子之间的交换相互作用消失.当量子点中掺入2个磁离子时,电子与Mn离子的sp-d相互作用会出现奇偶振荡行为,Mn离子间的相互作用取决于Mn离子间距和量子点壳层中的电子数,表现出典型的Ruderman-Kittel-Kasuya-Yosida型间接交换机制.工作澄清了拓扑绝缘体量子点壳层结构对其磁性的影响,有助于人们设计基于拓扑绝缘体量子点的自旋电子学或量子信息器件.

Magnetic exchange interactions in topological insulator quantum dots

We theoretically study the magnetic exchange interaction in topological insulator quantum dots. The number of electrons in topological edge states can be controlled by the size of the quantum dot and the applied electric field. When a single magnetic ion dopes the quantum dot, the edge state is filled with an odd number of electrons, and the exchange interaction between the electron and the magnetic ion reaches the maximum. When the edge state is filled with an even number of electrons, the exchange interaction disappears. When two magnetic ions dope the quantum dots, the sp-d interaction between electrons and ions exhibits odd-even oscillation behavior. The interaction between ions depends on the distance between the ions and the number of electrons in the quantum dot, which shows the typical Ruderman-Kittel-Kasuya-Yosida type indirect exchange mechanism. This work clarifies the influence of the shell structure of topological insulator quantum dots on its magnetic properties and can be helpful to design spintronics or quantum information devices based on topological insulator quantum dots.