Interacting Shiba States on Proximitized Superconducting Surface of Bi

Magnetic atoms on the surface of a superconductor induce in-gap Shiba states that can be hybridized to create a topological superconducting phase when placed in one-dimensional chains, with Majorana zero modes localized at their ends [1,2]. We have performed measurements of magnetic adatoms deposited on the surface of epitaxially grown Bi(110) thin films on a superconducting Nb(110) surface using a dilution refrigerator scanning tunneling microscope (STM). Our spectroscopic measurements show the Bi surface to exhibit a hard superconducting gap of 1.6 meV and the presence of Shiba states near magnetic adatoms. Using atomic manipulation techniques with the STM, we have built dimers of magnetic atoms with varying distance and geometry and detected the hybridization of individual in-gap states into “Shiba molecules”. We will report on these results and our efforts to build chains of magnetic atoms on the surface of superconducting Bi. The strong spin-orbit coupling and the large induced superconducting gap by the Nb substrate make this Bi surface an attractive platform for creation of atomic chains that host Majorana zero modes.

[1] S. Nadj-Perge et al. Phys. Rev. B (2013)
[2] S. Nadj-Perge et al. Science (2014)