利用光电子能谱测量FeSe/Nb:SrTiO₃/KTaO₃异质结构中应变FeSe单层的增强超导相和明显的能隙各向异性。

Measurement of an enhanced superconducting phase and a pronounced anisotropy of the energy gap of a strained FeSe single layer in FeSe/Nb:SrTiO3/KTaO3 heterostructures using photoemission spectroscopy.

作者信息

Peng R, Shen X P, Xie X, Xu H C, Tan S Y, Xia M, Zhang T, Cao H Y, Gong X G, Hu J P, Xie B P, Feng D L

机构信息

State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.

State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, China and Key Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200433, China.

出版信息

Phys Rev Lett. 2014 Mar 14;112(10):107001. doi: 10.1103/PhysRevLett.112.107001. Epub 2014 Mar 11.

DOI:10.1103/PhysRevLett.112.107001

PMID:24679321

Abstract

Single-layer FeSe films with an extremely expanded in-plane lattice constant of 3.99±0.02 Å are fabricated by epitaxially growing FeSe/Nb:SrTiO3/KTaO3 heterostructures and studied by in situ angle-resolved photoemission spectroscopy. Two elliptical electron pockets at the Brillouin zone corner are resolved with negligible hybridization between them, indicating that the symmetry of the low-energy electronic structure remains intact as a freestanding single-layer FeSe, although it is on a substrate. The superconducting gap closes at a record high temperature of 70 K for the iron-based superconductors. Intriguingly, the superconducting gap distribution is anisotropic but nodeless around the electron pockets, with minima at the crossings of the two pockets. Our results place strong constraints on current theories.

摘要

通过外延生长FeSe/Nb:SrTiO3/KTaO3异质结构制备出具有3.99±0.02 Å的极度扩展面内晶格常数的单层FeSe薄膜，并通过原位角分辨光电子能谱对其进行研究。在布里渊区角分辨出两个椭圆形电子口袋，它们之间的杂化可忽略不计，这表明尽管单层FeSe处于衬底上，但其低能电子结构的对称性仍保持为独立单层时的完整状态。对于铁基超导体，超导能隙在创纪录的70 K高温下闭合。有趣的是，超导能隙分布是各向异性的，但在电子口袋周围无节点，在两个口袋的交叉处有最小值。我们的结果对当前理论施加了严格限制。