CIC nanoGUNE, 20018 San Sebastián-Donostia, Spain.
Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, The Netherlands.
Nat Commun. 2017 May 8;8:15175. doi: 10.1038/ncomms15175.
A magnetic atom inside a superconductor locally distorts superconductivity. It scatters Cooper pairs as a potential with broken time-reversal symmetry, leading to localized bound states with subgap excitation energies, named Shiba states. Most conventional approaches regarding Shiba states treat magnetic impurities as point scatterers with isotropic exchange interaction. Here, we show that the number and the shape of Shiba states are correlated to the spin-polarized atomic orbitals of the impurity, hybridized with the superconductor. Using scanning tunnelling spectroscopy, we spatially map the five Shiba excitations found on subsurface chromium atoms in Pb(111), resolving their particle and hole components. While particle components resemble d orbitals of embedded Cr atoms, hole components differ strongly from them. Density functional theory simulations correlate the orbital shapes to the magnetic ground state of the atom, and identify scattering channels and interactions, all valuable tools for designing atomic-scale superconducting devices.
在超导体内部，一个磁性原子会局部扭曲超导性。它作为一个具有时间反演对称性破缺的势散射库珀对，导致具有亚带隙激发能的局域束缚态，称为希巴态。关于希巴态的大多数常规方法将磁性杂质视为各向同性交换相互作用的点散射体。在这里，我们表明希巴态的数量和形状与与超导体杂化的杂质的自旋极化原子轨道有关。使用扫描隧道光谱技术，我们在 Pb(111) 中的表面下铬原子上空间映射了五个希巴激发，解析了它们的粒子和空穴分量。虽然粒子分量类似于嵌入 Cr 原子的 d 轨道，但空穴分量与它们有很大的不同。密度泛函理论模拟将轨道形状与原子的磁基态相关联，并确定散射通道和相互作用，所有这些都是设计原子尺度超导器件的有价值的工具。
