论文标题

增强的Majorana绑定状态在超导拓扑绝缘子边缘的磁链中

Enhanced Majorana bound states in magnetic chains on superconducting topological insulator edges

论文作者

Teixeira, Raphael L. R. C., Kuzmanovski, Dushko, Black-Schaffer, Annica M., da Silva, Luis G. G. V. Dias

论文摘要

凝结物质系统中主要结合状态(MBS)形成的最有前途的机制涉及一维系统(例如半导体纳米线,磁链和量子旋转霍尔绝缘子(QSHI)边缘(QSHI)边缘),该系统可能会仿制为超导材料。这些选项中的每一个之间的选择都涉及几个因素之间的权衡,例如结果的可重复性,系统可调性和结果MBS的鲁棒性。在本文中,我们建议其中两个系统的组合,即与超导表面接触的QSHI边缘上的磁链,与在整体上沉积的磁性链相比,可以更好地选择可调性和MBS鲁棒性。我们研究QSHI边缘如何与磁链相互作用,并查看拓扑阶段如何受边缘接近度的影响。我们表明,与大体内部的MBS相比,在边缘附近的MBS可以用较低的化学势和Zeeman场实现,而与链的磁性秩序(铁磁或螺旋顺序)无关。链中的不同磁性订单修改了整体图,甚至抑制了位于QSHI边缘的链中的整体中发现的无限拓扑相。此外,我们通过计算不同配置的Majoraana极化(MP)来量化MBS的“质量”。对于位于边缘的链条,MP接近其短链的最大值。对于远离边缘的链条,需要更长的链条才能达到与边缘的链条相同的质量。 MP还与间隙状态相相位振荡,这是相对出乎意料的,因为能量光谱中的峰对应于MBS的更强重叠。

The most promising mechanisms for the formation of Majorana bound states (MBSs) in condensed matter systems involve one-dimensional systems (such as semiconductor nanowires, magnetic chains, and quantum spin Hall insulator (QSHI) edges) proximitized to superconducting materials. The choice between each of these options involves trade-offs between several factors such as reproducibility of results, system tunability, and robustness of the resulting MBS. In this article, we propose that a combination of two of these systems, namely a magnetic chain deposited on a QSHI edge in contact with a superconducting surface, offers a better choice of tunability and MBS robustness compared to magnetic chain deposited on bulk. We study how the QSHI edge interacts with the magnetic chain, and see how the topological phase is affected by edge proximity. We show that MBSs near the edge can be realized with lower chemical potential and Zeeman field than the ones inside the bulk, independently of the chain's magnetic order (ferromagnetic or spiral order). Different magnetic orderings in the chain modify the overall phase diagram, even suppressing the boundless topological phase found in the bulk for chains located at the QSHI edge. Moreover, we quantify the "quality" of MBSs by calculating the Majorana Polarization (MP) for different configurations. For chains located at the edge, the MP is close to its maximum value already for short chains. For chains located away from the edge, longer chains are needed to attain the same quality as chains located at the edge. The MP also oscillates in phase with the in-gap states, which is relatively unexpected as peaks in the energy spectrum corresponds to stronger overlap of MBSs.

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