Zaki Nader, Gu Genda, Tsvelik Alexei, Wu Congjun, Johnson Peter D
Condensed Matter Physics and Materials Science Division (CMPMSD), Brookhaven National Laboratory, Upton, NY 11973.
Department of Physics, University of California, San Diego, CA 92093.
Proc Natl Acad Sci U S A. 2021 Jan 19;118(3). doi: 10.1073/pnas.2007241118.
Topological superconductivity has been sought in a variety of heterostructure systems, the interest being that a material displaying such a phenomenon could prove to be the ideal platform to support Majorana fermions, which in turn could be the basis for advanced qubit technologies. Recently, the high-T family of superconductors, FeTeSe, have been shown to exhibit the property of topological superconductivity and further, evidence has been found for the presence of Majorana fermions. We have studied the interplay of topology, magnetism, and superconductivity in the FeTe Se family using high-resolution laser-based photoemission. At the bulk superconducting transition, a gap opens at the chemical potential as expected. However, a second gap is observed to open at the Dirac point in the topological surface state. The associated mass acquisition in the topological state points to time-reversal symmetry breaking, probably associated with the formation of ferromagnetism in the surface layer. The presence of intrinsic ferromagnetism combined with strong spin-orbit coupling provides an ideal platform for a range of exotic topological phenomena.
人们已在多种异质结构系统中探寻拓扑超导性，其意义在于，呈现这种现象的材料可能被证明是支持马约拉纳费米子的理想平台，而马约拉纳费米子反过来又可能成为先进量子比特技术的基础。最近，高温超导体系FeTeSe已被证明具有拓扑超导特性，并且进一步发现了存在马约拉纳费米子的证据。我们利用基于高分辨率激光的光电子能谱研究了FeTeSe体系中拓扑、磁性和超导性之间的相互作用。在体超导转变时，如预期的那样，化学势处出现了一个能隙。然而，在拓扑表面态的狄拉克点处观察到第二个能隙打开。拓扑态中相关的质量获取表明时间反演对称性被打破，这可能与表面层中铁磁性的形成有关。本征铁磁性与强自旋轨道耦合的存在为一系列奇异的拓扑现象提供了理想平台。
