Observation of Yu-Shiba-Rusinov-like states at the edge of CrBr3/NbSe2 heterostructure

The hybrid ferromagnet-superconductor heterostructures have attracted extensive attention as they potentially host topological superconductivity. Relevant experimental signatures have recently been reported in CrBr 3 /NbSe 2 ferromagnet-superconductor heterostructure, but controversies remain. Here, we reinvestigate CrBr 3 /NbSe 2 by an ultralow temperature scanning tunneling microscope with higher spatial and energy resolutions. We find that the single-layer CrBr 3 film is insulating and acts likely as a vacuum barrier, the measured superconducting gap and vortex state on it are nearly the same as those of NbSe 2 substrate. Meanwhile, in-gap features are observed at the edges of CrBr 3 island, which display either a zero-energy conductance peak or a pair of particle-hole symmetric bound states. They are discretely distributed at the edges of CrBr 3 film, and their appearance is found closely related to the atomic lattice reconstruction near the edges. By increasing tunneling transmissivity, the zero-energy conductance peak quickly splits, while the pair of nonzero in-gap bound states first approach each other, merge, and then split again. These behaviors are unexpected for Majorana edge modes, but in consistent with the conventional Yu-Shiba-Rusinov states. Our results provide critical information for further understanding the interfacial coupling in CrBr 3 /NbSe 2 heterostructure. There has been substantial interest in realizing topological superconductivity, with various systems being considered as potential hosts. Heterostructures such as CrBr 3 /NbSe 2 are one example. Here, Li and coauthors show, via scanning tunnelling microscope measurements, that signatures hitherto associated with topological superconductivity in CrBr 3 /NbSe 2 are consistent with a topologically trivial superconductor.