论文标题
二阶拓扑绝缘子和超导体中有限状态富含的可调性
Sublattice-enriched tunability of bound states in second-order topological insulators and superconductors
论文作者
论文摘要
尖锐角处的绑定状态已被广泛视为二维二阶拓扑绝缘子和超导体的标志。在这项工作中，我们表明，自由度的统一程度的存在可以丰富边界上约束状态的可调性，从而消除了其位置的约束。我们采用具有蜂窝状晶格结构的凯恩 - 梅勒模型来说明潜在的物理。随着对模型的平面交换字段的引入，我们发现由交换场引起的边界dirac质量对边界sublattice终止具有敏感的依赖性。我们发现，如果交换场具有铁电磁性质，即使在边界上没有任何锋利的角落，敏感的sublatice依赖性可能会导致绑定状态在特定类型的边界缺陷处出现，称为Sublattice域壁。值得注意的是，边界dirac质量对边界sublattice终止的敏感依赖性使得可以将界定状态的位置操纵到边界上的任何位置，以进行适当设计的样品。通过进一步引入模型的常规S波超导性，我们发现，无论交换场是否是铁磁，反铁磁性或铁磁性的，在Sublattice域壁上都可以实现高度可控制的Majora零模式。我们的工作重塑了对二阶拓扑阶段边界物理的理解，同时开放了潜在的途径，以实现潜在应用的高度可控的约束状态。
Bound states at sharp corners have been widely viewed as the hallmark of two-dimensional second-order topological insulators and superconductors. In this work, we show that the existence of sublattice degrees of freedom can enrich the tunability of bound states on the boundary and hence lift the constraint on their locations. We take the Kane-Mele model with honeycomb-lattice structure to illustrate the underlying physics. With the introduction of an in-plane exchange field to the model, we find that the boundary Dirac mass induced by the exchange field has a sensitive dependence on the boundary sublattice termination. We find that the sensitive sublattice dependence can lead bound states to emerge at a specific type of boundary defects named as sublattice domain walls if the exchange field is of ferromagnetic nature, even in the absence of any sharp corner on the boundary. Remarkably, this sensitive dependence of the boundary Dirac mass on the boundary sublattice termination allows the positions of bound states to be manipulated to any place on the boundary for an appropriately-designed sample. With a further introduction of conventional s-wave superconductivity to the model, we find that, no matter whether the exchange field is ferromagnetic, antiferromagnetic, or ferrimagnetic, highly controllable Majorana zero modes can be achieved at the sublattice domain walls. Our work reshapes the understanding of boundary physics in second-order topological phases, and meanwhile opens potential avenues to realize highly controllable bound states for potential applications.
