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arXiv 2408.02008cond-mat.supr-con
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通过高阶 Rashba 自旋轨道耦合工程多重 Majorana Kramers 对的螺旋超导体

Engineering Helical Superconductors with Multiple Majorana Kramers Pairs via Higher-Order Rashba Spin-Orbit Coupling

Chongqing University(重庆大学);Soochow University(苏州大学);Zhejiang University(浙江大学)

Qi-Sheng Xu, Zi-Ming Wang, Chui-Zhen Chen, Lun-Hui Hu, Rui Wang, Dong-Hui Xu

AI总结:

本文通过高阶 Rashba 自旋轨道耦合设计出具有多个 Majorana Kramers 对的二维螺旋超导体,突破了传统 Z₂ 分类和奇数费米面限制,展示了镜像陈数和 Kramers 对的显著提升。

摘要:

Rashba 自旋轨道耦合(RSOC)的动量依赖性是工程拓扑超导体(TSCs)的关键要素,但研究主要集中在线性动量形式上。这种关注限制了时间反演对称 TSCs 为 helical p-波态,其特征是 Z₂ 拓扑不变量,允许每个边界最多一个 Majorana Kramers 对。其存在也与严格的奇数费米面(FSs)数量条件相关。在本工作中,我们确立了高阶 RSOC 作为超越 Z₂ 分类和奇数 FS 条件的强大设计原则。我们证明了具有纯立方 RSOC 和单个 FS 上内在奇数 parity 配对的双层系统可产生罕见的二维 helical f-波 TSC。该状态特征大镜像陈数(MCN)为 N_M=3,且宿主三个 Kramers 对的 Majorana 边缘模式。值得注意的是,这种双层中线性和立方 RSOC 的相互作用可生成具有更大 MCN 为 N_M=4 的 helical 混合 p+f-波 TSC,从具有两个 FS 的正常态出发,从而绕过传统奇数 FS 条件。我们的工作确立了高阶 RSOC 作为实现具有多个 Majorana Kramers 通道的 TSCs 的“拓扑乘数”,从根本上重塑了 helical TSCs 的标准,并对如氧化物异质结构等可调平台具有即时相关性。

英文摘要:

The momentum dependence of Rashba spin-orbit coupling (RSOC) is a key ingredient for engineering topological superconductors (TSCs), yet research has overwhelmingly focused on its linear-in-momentum form. This focus has restricted time-reversal invariant TSCs to helical $p$-wave states, which are characterized by a $\mathbb{Z}_2$ topological invariant that permits at most a single Majorana Kramers pair at a given boundary. Their existence has also been tied to the stringent criterion of an odd number of Fermi surfaces (FSs). In this work, we establish higher-order RSOC as a powerful design principle to go beyond the $\mathbb{Z}_2$ classification and the odd-FS criterion. We demonstrate that a bilayer system with a pure cubic RSOC and an intrinsic odd-parity pairing on a single FS yields a rare 2D helical $f$-wave TSC. This state is characterized by a large mirror Chern number (MCN) of ${\cal N}_{\text{M}}=3$ and hosts three Kramers pairs of Majorana edge modes. Remarkably, the interplay of linear and cubic RSOCs in this bilayer can generate a helical hybrid $p+f$-wave TSC with an even larger MCN of ${\cal N}_{\text{M}}=4$ from a normal state with two FSs, thereby circumventing the conventional odd-FS criterion. Our work establishes higher-order RSOC as a "topology multiplier" for realizing TSCs with multiple Majorana Kramers channels, fundamentally reshapes the criteria for helical TSCs, and holds immediate relevance for tunable platforms like oxide heterostructures.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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