Spin-polarized zero bias peak from a single magnetic impurity at a s-wave superconductor

Topological superconductivity has emerged a promising platform for fault-tolerant quantum computing using Majorana modes. Since intrinsic topological superconductors are rare, various heterostructures including ferromagnetic atomic chains on s-wave superconductors were proposed to realize topological superconductivity. So far, most theoretical studies in the heterostructures were done using effective models based on single orbitals. We investigate the Yu-Shiba-Rusinov (YSR) states of a single magnetic impurity (Fe, Co, Mn) at the surface of superconducting Pb using the fully relativistic first-principles simulations including band structure of Pb and 3d orbitals of the impurity in the superconducting state. For the single Fe and Co impurities, we observe strong effects of spin-orbit coupling on the YSR states as the impurity moment rotates. As the rotation angle varies, we show that two symmetric YSR peaks merge and form a zero-bias peak with large spin polarization, although effective models predict zero normalized spin polarization for such a zero-bias peak. Our results reveal importance of realistic band structure and multiple 3d orbitals of the impurity in the calculations, and they are relevant to longer atomic chains considering canting and noncollinear magnetism.