Gao Yu-Mei, Huang Yi-Fei, Chi Feng, Yi Zi-Chuan, Liu Li-Ming
School of Electronic and Information Engineering, UEST of China, Zhongshan Institute, Zhongshan 528400, China.
School of General Education, Quanzhou Ocean Institute, Quanzhou 362700, China.
Nanomaterials (Basel). 2025 Sep 3;15(17):1359. doi: 10.3390/nano15171359.
Electronic transport through T-shaped double quantum dots (TDQDs) connected to normal metallic leads is studied theoretically by using a nonequilibrium Green's function method. It is assumed that the Coulomb interaction exists only in the central QD (QD-1) sandwiched between the leads, and it is absent in the other reference QD (QD-2) side-coupled to QD-1. We also consider the impacts of Majorana bound states (MBSs), which are prepared at the opposite ends of a topological superconductor nanowire (hereafter called a Majorana nanowire) connected to QD-2, on the electrical current and differential conductance. Our results show that by the combined effects of the Coulomb interaction in QD-1 and the MBSs, a negative differential conductance (NDC) effect emerges near the zero-bias point, where MBSs play significant roles. Now, the electrical current decreases despite the increasing bias voltage. The NDC is prone to occur under conditions of low temperature, and both of the two QDs' energy levels are resonant to the leads' zero Fermi energy. Its magnitude, which is characterized by a peak-to-valley ratio, can be enhanced up to 3 by increasing the interdot coupling strength, and it depends on the dot-MBS hybridization strength nonlinearly. This prominent NDC combined with the previously found zero-bias anomaly (ZBA) of the differential conductance is useful in designing novel quantum electric devices, and it may also serve as an effective detection means for the existence of MBSs, which is still a challenge in solid-state physics.
采用非平衡格林函数方法，从理论上研究了连接到普通金属引线的T型双量子点（TDQD）中的电子输运。假设库仑相互作用仅存在于夹在引线之间的中央量子点（量子点-1）中，而在与量子点-1侧耦合的另一个参考量子点（量子点-2）中不存在。我们还考虑了在连接到量子点-2的拓扑超导体纳米线（以下称为马约拉纳纳米线）两端制备的马约拉纳束缚态（MBS）对电流和微分电导的影响。我们的结果表明，通过量子点-1中的库仑相互作用和MBS的联合效应，在零偏置点附近出现了负微分电导（NDC）效应，其中MBS起着重要作用。此时，尽管偏置电压增加，但电流却减小。NDC在低温条件下容易出现，并且两个量子点的能级都与引线的零费米能共振。其大小以峰谷比为特征，通过增加点间耦合强度可提高到3，并且它非线性地依赖于量子点-MBS杂化强度。这种显著的NDC与先前发现的微分电导的零偏置异常（ZBA）相结合，在设计新型量子电子器件方面很有用，并且它也可以作为检测MBS存在的有效手段，这在固态物理学中仍然是一个挑战。
