Majek Piotr, Weymann Ireneusz
Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland.
Sci Rep. 2024 Aug 1;14(1):17762. doi: 10.1038/s41598-024-66478-z.
In this work we investigate the spin-dependent transport through a double quantum dot embedded in a ferromagnetic tunnel junction and side attached to a topological superconducting nanowire hosting Majorana zero-energy modes. We focus on the transport regime when the Majorana mode leaks into the double quantum dot competing with the two-stage Kondo effect and the ferromagnetic-contact-induced exchange field. In particular, we determine the system's spectral properties and analyze the temperature dependence of the spin-resolved linear conductance by means of the numerical renormalization group method. Our study reveals unique signatures of the interplay between the spin-resolved tunneling, the Kondo effect and the Majorana modes, which are visible in the transport characteristics. In particular, we uncover a competing character of the coupling to topological superconductor and that to ferromagnetic leads, which can be observed already for very low spin polarization of the electrodes. This is signaled by an almost complete quenching of the conductance in one of the spin channels which is revealed through perfect conductance spin polarization. Moreover, we show that the conductance spin polarization can change sign depending on the magnitude of spin imbalance in the leads and strength of interaction with topological wire. Thus, our work demonstrates that even minuscule spin polarization of tunneling processes can have large impact on the transport properties of the system.
在这项工作中，我们研究了通过嵌入铁磁隧道结并侧面连接到承载马约拉纳零能模的拓扑超导纳米线的双量子点的自旋相关输运。我们关注的是马约拉纳模泄漏到双量子点中与两阶段近藤效应和铁磁接触诱导的交换场竞争时的输运状态。特别是，我们通过数值重整化群方法确定了系统的光谱特性，并分析了自旋分辨线性电导的温度依赖性。我们的研究揭示了自旋分辨隧穿、近藤效应和马约拉纳模之间相互作用的独特特征，这些特征在输运特性中是可见的。特别是，我们发现了与拓扑超导体的耦合和与铁磁引线的耦合之间的竞争特性，这在电极的自旋极化非常低时就可以观察到。这通过完美的电导自旋极化揭示出一个自旋通道中的电导几乎完全淬灭来表明。此外，我们表明电导自旋极化可以根据引线中的自旋不平衡幅度和与拓扑线的相互作用强度改变符号。因此，我们的工作表明，即使隧穿过程中极小的自旋极化也会对系统的输运性质产生很大影响。
