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中国物理学会期刊

正方Shiba晶格中的高阶拓扑超导研究

Higher-order topological superconductivity in a square Shiba lattice system

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  • 在无自旋轨道耦合的s波超导表面,磁通与吸附的磁性原子形成的反铁磁序的结合能够诱导高阶拓扑超导.然而,实际磁晶格中受多种因素影响,磁序往往偏离理想的反铁磁构型,产生不同类型的畸变.为此,本文在反铁磁模型中引入铁磁序与螺旋磁序作为畸变因素,系统探究该模型下的高阶拓扑超导性质,并深入剖析高阶拓扑态形成的物理根源.研究结果表明,反铁磁序是实现高阶拓扑超导的必要前提;铁磁序虽会重整能带结构,但不会破坏高阶拓扑能隙.相较之下,螺旋成分的加入会使能带发生倾斜畸变,一旦相邻磁矩间的夹角增大至临界值,能隙便完全闭合,拓扑态随之消失.

     

    On the surface of an s-wave superconductor without spin-orbit coupling, the combination of magnetic flux and antiferromagnetic order induced by adsorbed magnetic atoms can give rise to higher-order topological superconductivity. However, in realistic magnetic lattices, the magnetic order often deviates from the ideal antiferromagnetic configuration due to various influencing factors, resulting in different types of distortions. To this end, this paper introduces ferromagnetic order and spiral magnetic order as distortion factors into the antiferromagnetic model, systematically investigates the higher-order topological superconducting properties of this model, and thoroughly analyzes the physical origin of the higher-order topological states. We employ the quadrupole moment topological invariant to demonstrate that the boundary corner states are higher-order topological corner states. Meanwhile, we understand the formation mechanism of the topological corner states from the perspective of the low-energy boundary effective Hamiltonian. The results show that antiferromagnetic order is a prerequisite for realizing higher-order topological superconductivity; although ferromagnetic order renormalizes the band structure, it does not destroy the higher-order topological gap. In contrast, the introduction of a spiral component causes a tilting distortion of the energy bands. Once the angle between adjacent magnetic moments increases to a critical value, the energy gap completely closes and the topological states vanish accordingly.

     

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