狭窄的二维拓扑绝缘体超导结中新奇的0-π态转变  

Novel 0-π State Transitions in a Superconducting Narrow Two-Dimensional Topological Insulator Junction

作　　者：俞清云 陶永春[1] 

机构地区：[1]南京师范大学物理科学与技术学院,江苏南京210023

出　　处：《南京师大学报（自然科学版）》2017年第3期87-93,共7页Journal of Nanjing Normal University(Natural Science Edition)

基　　金：江苏省普通高校研究生科研创新计划项目(KYLX16_1266)

摘　　要：边间耦合引起的边间背散射是赋予狭窄的二维拓扑绝缘体的重要特性,能够大大地丰富拓扑超导电子学.本文在考虑边间耦合的情况下,使用基于Bogoliubov-de Gennes(BdG)方程的理论方法,研究了由狭窄的二维拓扑绝缘体构成的Josephson结,其中两个相距长度为d的超导电极置于同一边上.结果发现,通过改变d总可以导致0-π态转变,同时这0-π态转变能反过来证明边缘态螺旋性的自旋结构.引起这个新奇的结果的机制源于边间背散射引诱了一个额外的π相移,不同于由两个超导电极间铁磁体夹层厚度变化所引起的传统的0-π态转变.此外,在0-π态转变点处存在相当大的Josephson临界电流残余值.因此,这些结果在超导电子学器件的设计中具有潜在的应用价值,譬如,高性能的超流开关.The narrow two-dimensional topological insulator is characterized by the interedge backscattering originating from interedge coupling, which could greatly enrich topological superconducting electronics. Here, considering the interedge coupling,we apply Bogoliubov-de Gennes（ BdG）equation to study the Josephson junction composed of a narrow two-dimen-sional topological insulator strip,where two superconducting electrodes at a distance of d are placed on the same edge of the strip. It is found that varying d could give rise to a 0-π state transition, which in turn can manifest the helical spin texture of the edge states. The mechanism stems from an additional 77 phase shift caused by the interedge backscattering, being different from the conventional one induced by the length of the ferromagnet sandwiched between two superconducting elec-trodes. Moreover,an unusually large residual value of the Josephson critical current at the 0- π state transition point is always exhibited. As a result,the results have potential applications in the designs of superconducting electronic devices,for instance,a supercurrent switch with a very efficient performance.

关 键 词：狭窄的二维拓扑绝缘体 边间耦合 JOSEPHSON结 0-π态转变 

分 类 号：O469[理学—凝聚态物理] O511.9[理学—电子物理学]