One-dimensional topological superconductivity at the edges of twisted bilayer graphene nanoribbons
One-dimensional topological superconductivity at the edges of twisted bilayer graphene nanoribbons
复制标题
扭曲双层石墨烯纳米带边缘的一维拓扑超导性
DOI：
10.1103/physrevb.100.094531
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发表时间：
2019
影响因子：
3.7
通讯作者：
Chen Wei Qiang
中科院分区：
文献类型：
--
作者：
Wang Zhen Hua;Xu Fuming;Li Lin;Lu Rong;Wang Bin;Chen Wei Qiang
扭曲双层石墨烯是最简单的货车德瓦尔斯结构之一，其非均匀层间耦合可以诱导出丰富的电子性质。在扭曲双层石墨烯纳米带（tBLGNRs）中，由于非均匀成键，带的两个边缘的层间耦合强度不同，边缘态在能量上分裂为两个个体.在Rashba自旋-轨道耦合、塞曼场和波超导的存在下，位于带边缘的低能态具有较强的层间耦合，是产生一维（1D）拓扑超导性的良好候选者。马约拉纳零模式（MZMs）被发现本地化在这条边的两端。通过计算无限长带的Berry相位和准一维带的Majorana极化，研究了系统的拓扑不变量，给出了相同的拓扑相图。更重要的是，通过调整层间位错和tBLGNRs的单轴应变跨越临界值，较低能量的边缘变化和一维拓扑超导性可以从一个带边“跳”到另一个带边。最后，通过在双层之间施加栅极偏压或改变层间距离，MZM可以沿着带边缘转移。tBLGNRs为研究一维拓扑超导性和MZM提供了一个替代平台。
Twisted bilayer graphene is one of the simplest van der Waals structures, and its inhomogeneous interlayer coupling can induce rich electronic properties. In twisted bilayer graphene nanoribbons (tBLGNRs), the interlayer coupling strengths are different for two ribbon edges due to the inhomogeneous bonding, which splits the edge states into two individuals in energy. The lower-energy state, localizing at the ribbon edge with the stronger interlayer coupling, is a good candidate to generate one-dimensional (1D) topological superconductivity in the presence of Rashba spin-orbit coupling, Zeeman field, and-wave superconductivity. Majorana zero modes (MZMs) are found to be localized at both ends of this edge. The topological invariants of the system are explored by evaluating the Berry phase for infinite-length ribbons and Majorana polarization for quasi-1D ribbons, giving the same topological phase diagram. More importantly, by adjusting interlayer dislocation and uniaxial strain of tBLGNRs across the critical values, the lower-energy edge changes and 1D topological superconductivity can “jump” from one ribbon edge to the other one. Finally, by applying a gate voltage bias between bilayers or changing the interlayer distance, a MZM can transfer along the ribbon edge. The tBLGNRs provide an alternative platform to study 1D topological superconductivity and MZMs.