Zhang Tianzhen, Bao Weicheng, Chen Chen, Li Dong, Lu Zouyuwei, Hu Yining, Yang Wentao, Zhao Dongming, Yan Yajun, Dong Xiaoli, Wang Qiang-Hua, Zhang Tong, Feng Donglai
State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200438, China.
National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing 210093, China.
Phys Rev Lett. 2021 Mar 26;126(12):127001. doi: 10.1103/PhysRevLett.126.127001.
The energy and spatial distributions of vortex bound state in superconductors carry important information about superconducting pairing and the electronic structure. Although discrete vortex states, and sometimes a zero energy mode, had been observed in several iron-based superconductors, their spatial properties are rarely explored. In this study, we used low-temperature scanning tunneling microscopy to measure the vortex state of (Li,Fe)OHFeSe with high spatial resolution. We found that the nonzero energy states display clear spatial oscillations with a period corresponding to bulk Fermi wavelength; while in contrast, the zero energy mode does not show such oscillation, which suggests its distinct electronic origin. Furthermore, the oscillations of positive and negative energy states near E_{F} are found to be clearly out of phase. Based on a two-band model calculation, we show that our observation is more consistent with an s_{++} wave pairing in the bulk of (Li, Fe)OHFeSe, and superconducting topological states on the surface.
超导体中涡旋束缚态的能量和空间分布承载着有关超导配对和电子结构的重要信息。尽管在几种铁基超导体中已经观测到离散的涡旋态，有时还观测到零能量模式，但其空间特性却很少被探究。在本研究中，我们使用低温扫描隧道显微镜以高空间分辨率测量了(Li,Fe)OHFeSe的涡旋态。我们发现，非零能量态呈现出清晰的空间振荡，其周期对应于体费米波长；而相比之下，零能量模式并未表现出这种振荡，这表明其电子起源不同。此外，发现费米能级附近正负能量态的振荡明显异相。基于双带模型计算，我们表明我们的观测结果与(Li, Fe)OHFeSe体中的s++波配对以及表面上的超导拓扑态更为一致。
