铁磁性电极条件下T形双量子点结构中马约拉纳束缚态的解耦现象

Decoupling of Majorana bound states in T-shaped doublequantumdot structure with ferromagnetic leads

通过将马约拉纳束缚态侧耦合到主通道中的量子点,从理论上研究了T形双量子点体系的输运性质.结果表明,调整侧耦合量子点能级和量子点-马约拉纳束缚态耦合方式,可以在线性输运区观察到马约拉纳束缚态与T形双量子点解耦的现象.引入铁磁性电极后,电导平台的出现或损坏明显依赖于体系中磁场与电极极化方向的差异,而马约拉纳束缚态的解耦现象仍然稳固.本工作有助于进一步诠释T形双量子点体系中马约拉纳束缚态的解耦现象,为深入认知以及探测马约拉纳束缚态提供理论支持.

The significant potential applications of Majorana bound state(MBS)in topological quantum computing manifest the importance and necessity of relevant in-depth research.To understand the physical properties of MBS,the most practical approach is to integrate it to a mesoscopic circuit and then investigate its quantum transport behaviors.In this work,we investigate the transport properties in the systems with MBS,and provide theoretical support for its further understanding and detection,by utilizing the nonequilibrium Green’s function method and scattering matrix theory.Specifically,we investigate theoretically the transport properties in a T-shaped double-quantum dot structure,by considering MBS to be coupled to the dot in the main channel,which shows that in the linear transmission region,when the level of side-coupled dot is tuned to the Fermi energy level,the contribution of MBS to the conductance is eliminated under weak and strong Coulomb interaction.The side-coupled dot is far away from the Fermi energy level,leading to different results.When Majorana zero mode is added,the linear conductance is independent of the level of the side-coupled quantum dot,and the conductance plateau appears.However,with coupling between the MBSs,the linear conductance is the same as that without coupling between the MBSs.The decoupling phenomenon of the MBS remains strong.Therefore,the signature of the MBS can be eliminated by adjusting the level of the side-coupled quantum dot or the inter-MBS coupling.When ferromagnetic leads are introduced,the appearance or disappearance of the conductance plateau is clearly dependent on the difference between the magnetic field direction and the lead polarization direction in the system,whereas the decoupling behavior of the MBS is still existent.This work contributes to further explaining the decoupling phenomenon of MBSs in a T-shaped double-quantum-dot system,and presents a theoretical approach to more in-depth understanding and detection of the MBS.