Fully gapped topological surface states in Bi sub(2)Se sub(3) films induced by a d-wave high-temperature superconductor

• Published in: Nature physics 2013-10, Vol.9 (10), p.621-625
• Main Authors: Wang, Eryin, Ding, Hao, Fedorov, Alexei V, Yao, Wei, Li, Zhi, Lv, Yan-Feng, Zhao, Kun, Zhang, Li-Guo, Xu, Zhijun, Schneeloch, John, Zhong, Ruidan, Ji, Shuai-Hua, Wang, Lili, He, Ke, Ma, Xucun, Gu, Genda, Yao, Hong, Xue, Qi-Kun, Chen, Xi, Zhou, Shuyun
• Format: Article
• Language: English
• Subjects: CRYSTAL GROWTH; ELECTRICAL CONDUCTIVITY; EPITAXY; Fault tolerance; Fermions; Helical; Insulators; Molecular beam epitaxy; Platforms; SUPERCONDUCTIVITY; SUPERCONDUCTORS; Topology
• ISSN: 1745-2473
• DOI: 10.1038/nphys2744

Topological insulators are a new class of material, that exhibit robust gapless surface states protected by time-reversal symmetry. The interplay of such symmetry-protected topological surface states and symmetry-broken states (for example, superconductivity) provides a platform for exploring new quantum phenomena and functionalities, such as one-dimensional chiral or helical gapless Majorana fermions, and Majorana zero modes that may find application in fault-tolerant quantum computation. Inducing superconductivity on the topological surface states is a prerequisite for their experimental realization. Here, by growing high-quality topological insulator Bi sub(2)Se sub(3) films on a d-wave superconductor Bi sub(2)Sr sub(2)CaCu sub( 2)O sub(8+ delta ) using molecular beam epitaxy, we are able to induce high-temperature superconductivity on the surface states of Bi sub(2)Se sub(3) films with a large pairing gap up to 15meV. Interestingly, distinct from the d-wave pairing of Bi sub(2)Sr sub(2)CaCu sub( 2)O sub(8+ delta ), the proximity-induced gap on the surface states is nearly isotropic and consistent with predominant s-wave pairing as revealed by angle-resolved photoemission spectroscopy. Our work could provide a critical step towards the realization of the long sought Majorana zero modes.