Yang Xing, Yuan Yuan, Peng Yang, Minamitani Emi, Peng Lang, Xian Jing-Jing, Zhang Wen-Hao, Fu Ying-Shuang
School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China.
Nanoscale. 2020 Apr 21;12(15):8174-8179. doi: 10.1039/d0nr01383h. Epub 2020 Apr 3.
Yu-Shiba-Rusinov (YSR) states arise when magnetic impurities interact with superconductivity. The intricacy of coupling and the nature of the superconductivity determine the behavior of the YSR state, whose detailed correlations are not yet fully understood. Here, we study the YSR state of a single Fe adatom on the surface of 2H-NbSe with combined low temperature scanning tunneling microscopy/spectroscopy, density functional theory calculations and tight-binding modeling. It is found that the Fe adatom occupies the hollow site of the Se surface layer. A prominent YSR state close to the Fermi level is observed. The YSR state exhibits a threefold symmetry along the diagonal direction of the Se lattice. The spatial decay of the YSR state follows a behavior in three-dimensional superconductivity. This behavior contrasts with a previous study of imbedded Fe impurities, whose YSR state shows a six-fold symmetry and a two-dimensional long-range decay. According to our theoretical modeling, the coupling configurations affect the adatom-substrate hopping and the interlayer coupling of the substrate. Both factors are crucial for the consequent behavior of the YSR state.
当磁性杂质与超导性相互作用时会出现汤浅-柴田-鲁西诺夫（YSR）态。耦合的复杂性和超导性的本质决定了YSR态的行为，其详细的相关性尚未完全理解。在此，我们结合低温扫描隧道显微镜/光谱、密度泛函理论计算和紧束缚模型，研究了2H-NbSe表面单个铁吸附原子的YSR态。发现铁吸附原子占据了硒表面层的空穴位点。观察到一个靠近费米能级的显著YSR态。YSR态沿硒晶格的对角线方向呈现三重对称性。YSR态的空间衰减遵循三维超导中的行为。这种行为与之前对嵌入铁杂质的研究形成对比，其YSR态显示出六重对称性和二维长程衰减。根据我们的理论模型，耦合构型影响吸附原子与衬底之间的跃迁以及衬底的层间耦合。这两个因素对于YSR态随后的行为都至关重要。
