The Coexistence of Superconductivity and Topological Order in the Bi2Se3 Thin Films
The Coexistence of Superconductivity and Topological Order in the Bi2Se3 Thin Films
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Bi2Se3 薄膜中超导性与拓扑序的共存
DOI：
10.1126/science.1216466
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发表时间：
2012-04-06
期刊：
影响因子：
56.9
通讯作者：
Xue, Qi-Kun
中科院分区：
文献类型：
--
作者：
Wang, Mei-Xiao;Liu, Canhua;Xue, Qi-Kun
当被放置在超导体附近时，拓扑绝缘体(TIS)预计将支持Majorana费米子，这是一种奇异的粒子，是它们自己的反粒子。为了实现这一点，TI和超导层之间的界面必须在原子上尖锐，但在电子上是透明的。Wang等人。(第52页，3月15日在线发表)通过在覆盖有双层铋的超导体NbSe2上生长一层TI材料Bi2Se3来制作这种异质结构。扫描隧道谱显示，不同厚度的Bi2Se_3薄膜在异质结的TI表面形成超导带隙。这种超导电性和拓扑秩序的共存，现在应该可以观察到像Majorana费米子这样的奇异现象。在超导体表面生长了一层薄薄的拓扑绝缘体，获得了超导带隙。三维拓扑绝缘体具有非平凡的表面态，在时间反转对称性的保护下，电子的自旋与动量成直角锁定。TIS中的拓扑有序相不破坏任何对称性。拓扑有序和对称性破缺之间的相互作用，如在超导中观察到的那样，可以导致新的量子现象和器件。通过在三硒化铋(Bi2Se3)超导体衬底上生长三硒化铋(Bi2Se3)薄膜，制备了一种超导Ti/超导异质结。利用扫描隧道显微镜和角度分辨光电子能谱，在Bi2Se_3膜厚范围内观察到了形成拓扑表面态的Bi2Se_3表面的超导能隙。这一观察结果为在凝聚态物理中实验实现马约拉纳费米子奠定了基础。
All Set for Majoranas When put in the proximity of a superconductor, topological insulators (TIs) are expected to support Majorana fermions, exotic particles that are their own antiparticles. For this to be realized, the interface between the TI and superconductor layers has to be atomically sharp but electronically transparent. Wang et al. (p. 52, published online 15 March) fabricated this heterostructure by growing a film of the TI material Bi2Se3 on the superconductor NbSe2 covered with a Bi bilayer. Scanning tunneling spectroscopy revealed a superconducting gap on the TI surface of the heterostructure with varying thickness of the Bi2Se3 film. This coexistence of superconductivity and topological order should now allow observation of exotic phenomena such as Majorana fermions. A thin layer of a topological insulator grown on the surface of a superconductor is shown to acquire a superconducting gap. Three-dimensional topological insulators (TIs) are characterized by their nontrivial surface states, in which electrons have their spin locked at a right angle to their momentum under the protection of time-reversal symmetry. The topologically ordered phase in TIs does not break any symmetry. The interplay between topological order and symmetry breaking, such as that observed in superconductivity, can lead to new quantum phenomena and devices. We fabricated a superconducting TI/superconductor heterostructure by growing dibismuth triselenide (Bi2Se3) thin films on superconductor niobium diselenide substrate. Using scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we observed the superconducting gap at the Bi2Se3 surface in the regime of Bi2Se3 film thickness where topological surface states form. This observation lays the groundwork for experimentally realizing Majorana fermions in condensed matter physics.